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Volume 1, Number 4
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The magaz
David Ahl, Founder апа
Publisher of Creative Computing
You might think the term ‘creative com-
puting’ is a contradiction. How can some-
thing as precise and logical as electronic
computing possibly be creative? We think
itcan be. Consider the way computers are
being used to create special effects in
movies—image generation, coloring and
computer-driven cameras and props. Oran
electronic "sketchpad' for your home
computer that adds animation, coloring
and shading at your direction. How about a
computer simulation of an invasion of killer
bees with you trying to find a way of keep-
ing them under control?
Beyond Our Dreams
Computers are not creative per se. But
the way in which they are used can be
highly creative and imaginative. Five years
ago when Creative Computing magazine
first billed itself as "Тһе number 1 maga-
zine of computer applications and soft-
ware, we had no idea how far that idea
would take us. Today, these applications
are becoming so broad, so all-
encompassing that the computer field will
soon include virtually everything!
In light of this generality, we take "appli-
cation to mean whatever сап be done with
computers, ought to be done with comput-
ers or might be done with computers. That
is the meat of Creative Computing.
Alvin Toffler, author of Future Shock and
The Third Wave says, `| read Creative Com-
puting not only for information about how
to make the most of my own equipment but
to keep an eye on how the whole field is
emerging.
Creative Computing, the company as
well as the magazine, is uniquely light-
hearted but also seriously interested іп all
aspects of computing. Ours is the maga-
zine of software, graphics, games and sim-
ulations for beginners and relaxing profes-
sionals. We try to present the new and im-
portant ideas of the field in a way that a 14-
year old or a Cobol programmer can under-
stand them. Things like text editing, social
creative
A REMARKABLE MAGAZINE
compating
"The beat covered by Creative Computing
is one of the most important, explosive and
fast-changing.” — Alvin Toffler
simulations, control of household devices,
animation and graphics, and communica-
tions networks.
Understandable Yet Challenging
As the premier magazine for beginners, it
is our solemn responsibility to make what
we publish comprehensible to the new-
comer. That does not mean easy; our
readers like to be challenged. It means
providing the reader who has no prepar-
ation with every possible means to seize
the subject matter and make it his own.
However, we dont want the experts in
our audience to be bored. So we try to
pubiish articles of interest to beginners and
experts at the same time. Ideally, we would
like every piece to have instructional or
informative content—and some depth—
even when communicated humorously or
playfully. Thus, our favorite kind of piece is
acessible to the beginner, theoretically
non-trivial, interesting on more than one
level, and perhaps even humorous.
David Gerrold of Star Trek fame says,
"Creative Computing with its unpreten-
tious, down-to-earth lucidity encourages
the computer user to have fun. Creative
Computing makes it possible for me to
learn basic programming skills and use the
computer better than any other source.
Hard-hitting Evaluations
At Creative Computing we obtain new
computer systems, peripherals, and soft-
ware as soon as they are announced. We
put them through their paces in our Soft-
ware Development Center and also in the
environment for which they are intended —
home, business, laboratory, or school.
Our evaluations are unbiased and accur-
ate. We compared word processing printers
and found two losers among highly pro-
moted makes. Conversely, we found one
computer had far more than its advertised
capability. Of 16 educational packages,
only seven offered solid learning value.
When we say unbiased reviews we mean
it. More than once, our honesty has cost us
an advertiser — temporarily. But we feel
that our first obligation is to our readers and
that editorial excellence and integrity are
our highest goals.
Karl Zinn at the University of Michigan
feels we are meeting these goals when he
writes. "Creative Computing consistently
provides value in articles, product reviews
and systems comparisons ...in a magazine
that is fun to read."
Order Today
To order your subscription to Creative
Computing send payment to the appropri-
ate address below. Customers in the
continental U.S. may call toll-free to
charge a subscription to Visa, MasterCard
or American Express.
Canada and
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We guarantee your satisfaction or we
will refund your entire subscription price.
Join over 80,000 subscribers like Ann
Lewin, Director of the Capital Children's
Museum who says, “I am very much im-
pressed with Creative Computing. |t is
helping to demystify the computer. Its arti-
cles are helpfu!, humorous and humane.
The world needs Creative Computing.”
Greative
Gorepatirg
P.O. Box 789-M
Morristown, NJ 07960
Toll-free 800-631-8112
(іп NJ 201-540-0445)
27 Andrew Close, Stoke Golding
Nuneaton CV13 6EL, England
The magazine for Sinclair ZX80/1 users
Ei | ==
July/August 1981 Volume 1, Number 4
DEPARTMENTS GAMES AND PROGRAMS
2 Glitchoidz Report. .................................... 36 Ee ИЕ Nisbet
ind the clues
3 SYNC Могев................................. Grosjean
44 winiBillboard. |. Duke
4 Letters. oe Make your own sign
6 РегсерШіопв.................................. Ornstein
SYNCSUM MACHINE LANGUAGE
20 Puzzles and Problems....................... Townsend Machine Code Keyboard Scanning............Puerzer
2 8 Decoding the keyboard
Crash Сигзог.................................. Truman
1 6 Screen 5сто ћпд................................ Logan
46 ЖЕТЕ; везан ње био ров оба в А Third іп a series оп machine language
STRINGS AND ARRAYS INTERFACING
11 me TL$ Ғипсіоп............................... Miller | 12 rechniauesotthezxeo.......... ss Onsy
TL$ for “READ"ing Outputting to asynchronous peripherals
24 Multidimensional Arrays on the 2Х80........ O'Connell 38 A Parallel іпіегігсе................................ Salt
Dealing with DIM statements A construction project
26 TRS and LET А5-А5--В5 onthe ZX80......... Doakes REVIEWS AND RESOURCES
String handling without TR$ 45 ——— Utasi
же И asi
MATH AND MATH GRAPHICS Hardware Review
22 46 зквом _______._._____. Lubar
Setting Up Bar Сһагів.......................... Passler
Visual statistics Hardware Review
23 Bisection Iteration Square Root Program......... Goins 47 andthe Walls Came Tumbling Down.......... Grosjean
34
Find your roots
Тһе ZX80 Makes the Grade....................... Auer
Adding and analyzing statistics
Multiplication Three іп а Row................... Brown
Test your skill
Software Review
НВезоигссев.......................................
COVER: Young beginners at Creative Computing’s summer Computer
Camp learning Basic operations on the ZX80 keyboard. Photo
courtesy Morristown Daily Record.
incumbent eee не
Publisher/Editor-in-Chief
Editorial Director
Managing Editor
Associate
Secretary
Production Manager
Typesetters
Financial Coordinator
Bookkeeper
Customer Service
Order Processing
Circulation
MEMBER
Staff
Advertiser
David H. Ahl Are you in SYNC
George Blank
Paul Grosjean
Be a Computer Literate
Colossal Computer Cartoon Book 45
Index to Advertisers
Volume 1, Number 4
Page
үз SYNC is published bi-monthly for $10.00 per year
14 by Creative Computing, 39 E. Hanover Ave.. Mor-
ris Plains, NJ 07950. Second class postage paid at
Editor David Lubar Creative Computing Subscriptions Cover 2 Morris Plains, New Jersey 07950, and additional
Elizabeth Magin Find ZX80 owners 33 entry offices.
Laura MacKenzie Katie and the Computer 21
Jean Ann Vokoun Lamo-Lem 9 Postmaster: Send address changes to SYNC, P.O.
Maureen Welsh L.J.H. Enterprises 23 Box 789-M, Morristown, NJ 07960.
William L. Baumann Macronics 21
Patricia Kennelly Maples 33 Subscriptions in USA: 6 issues $10; 12 issues $18:
Ralph Loveys New England Software 13 18 issues $24. UK and foreign airmail subscrip-
Ruth Coles Peripherals Plus 33 tions: 6issues £10; 12 issues £18; 18 issues £25. Call
Frances Miskovich Softsync 23 (800) 631-8112 toll-free (іп NJ, 201-540-0445) to
Dorothy Staples SYNC Cover 4 begin your subscription.
Carol Vita Creative Computing T-Shirts Cover 3
Zeta Software 21 Copyright 1981 by Creative Computing. All rights
July/August 1981
reserved. Reproduction prohibited in any form.
neport
The GLITCHOIDZ REPORT will pass
on to our readers errors, problems, and
other Glitchoid activities which have been
discovered. We welcome your contribu-
tions to this column.
GOTO Lines
Some readers have asked about a line
such as GOTO 450 when the program
does not have a line 450. In the Z X80 this
does not stop the program or confuse the
computer. The ZX80 will search for the
line and, failing to find it, go on to the
next line in the program after 450. In
effect, it jumps over the GOTO command
line in such cases.
Castle Doors (1:30)
Correct:
48 IF D=2 THEN LET A=RND(30)
62 IF D=5 THEN LET A$=“ZOMBIE”
Draw a Picture (1:33)
Some readers have reported difficulties
with this program, but it will run as printed.
Pay especial attention to the last paragraph.
When the program is entered and RUN,
you are to respond to the prompt by
entering the coordinates of the square
you want to fill with a graphics symbol.
You are then to respond to the prompt
ENTER CHAR CODE with the number
of the symbol you want as shown in column
3. Erasing may be done by entering 0 to
erase the previous character or by entering
the coordinates again and then the new
character.
How to Produce a Display File
(2:15, col. 13
A full screen suggestion:
40 FOR J=1 TO 21
Correct:
60 FOR I=1 TO 30
70 PRINT * >; (1 sp.)
(2:15, col. 1)
Continue adding dummy lines until line
10 is scrolled off the screen. Then delete
the dummy lines by entering the line
number and NEWLINE before entering
the loader program.
(2:15, col. 2)
40 IFA «1 OR > 300 THEN GOTO 30
Truth in Programming (2:19, col. 1)
20 IF X THEN LET Т=Т+1
2
Glitchoidz 9%:
е
9 * x 3 0
SOLS
(098) —
КОВ
god pA?
EN SS uec e...
i iJ
Game of Life (2:29)
Change: 450 NEXT I
Add: 460 FOR 1=9 TO 55
The graphics given in the program do
not produce the * in the square. Hopefully
the * makes it easier to see the squares
being referred to. For those who want to
use the * in the display, change the
character number 128 to 222 in lines 120
and 500.
Some readers have pointed out that
the game does not follow the rules in the
article. Reader Walter Bacon has proposed
program changes to bring it closer to the
rules (see Letters).
Artillery (2:27)
Readers with 1K have found that the
game fills the memory rather quickly. You
can increase the memory available for
play by trimming down the PRINT state-
ments to very brief prompts or try Reader
Joe Dell'Orfano's program amendments
(see Letters).
Tic Tac Toe (2:22)
Add: 445 CLS
More Truth in Programming (3:7, col. 3)
Correct:
IF NOT (X <5 AND Y< 8)...
Black Hole (3:9)
Correct:
75 IF S<1 OR $ >9 THEN GOTO 70
See the Letters for suggestions for
trimming this to 1K.
Auto-Display-Changing (3:14)
Dr. Logan reports a bug that occurs
because of variations in TV sets: “Some
users may find it necessary to use other
values in line 64.
64 POKE A+24,3 ог 5
in order to get better timing.”
Variable Conversions (3:26)
Correct:
113 IF X=-27 THEN GOTO 116
Forest Treasure (3:34)
Correct:
30 PRINT ‘g’; (shift A), or
30 PRINT CHR$(128)
490 delete %
8K Basic ROM and 16K-Byte RAM Pack
(3:37)
As a number of readers observed, the
actual ROM they received differs somewhat
from our article. Between the time we
received the materials and the actual
production of the 8K ROM a few changes
were made.
The following
omitted:
DATA
DRAW m,n
NEW n
READ у
RESTORE
UNDRAW m,n
These commands were added:
LPRINT Prints a string on the printer.
commands were
L LIST Lists the program on the
printer.
COPY Prints the entire screen on
the printer. The printer is
capable of printing all the
characters including
graphics.
FAST On the ZX81 there are two
modes of operation.
SLOW On the ZX80 8K keyboard
these do not function.
(3:38)
16K RAM Pack: A separate power
supply is now being provided.
The ZX80 Keyboard
(3:42)
The author is David Ornstein, 25 Shute
Path, Newton Centre, MA 02159.
(3:44)
Listing 1 is copyrighted by Sinclair
Research.
Graphics Surprises (3:22)
The author is James H. Parsons, 1921
Flintlock Terrace West, Colorado Springs,
CO 80918.
SYNC Magazine
зло | = | $ = — ___6_(___
Раш Grosjean
ZX81 — The Family Increases
A number of people have asked us
whether we are going to include the ZX81
in our coverage. As our changed cover
shows, the answer is a definite YES.
With the multiplication of the ZX80
family and the availability of new ROMs
and RAMs, our readers want to know
what the machine requirements of our
programs are. If you are planning to send
us an article or program that you have
developed, be sure to state the minimum
machine requirements for your, program
on a separate line below the title. When
we are referring to the general family or
discussing the family in areas where the
ROMs and RAMs are not important, we
will say simply the “Z X80,” but where the
ROM and RAM are important we want
to include that information.
PERCEPTIONS
In this issue we are introducing the
column PERCEPTIONS by David Ornstein
(p.6 ). David has already contributed to
SYNC through his work on the schematic
of the Z X80 in issue 1, “Video Modifica-
tions for the ZX80” in issue 2, and “The
ZX80 Keyboard” in issue 3.
Though he is Technical Services
Manager for Sinclair Research Limited
(U.S.), we must hasten to point out that
the views expressed in his column will be
strictly his own and in no way will represent
Sinclair Research.
SYNCSUM
We are especially pleased with the first
contribution of PERCEPTIONS to SYNC
readers and authors in the concept and
programs for the SYNCSUM. This is a
method of checking whether you have
entered the program correctly. If you are
submitting an article, we ask you to include
the SYNCSUM at the end of any program
listing.
July/August 1981
Spaces in PRINT Statements
Since we do not have a symbol on the
ZX80 that marks clearly the empty spaces,
sometimes problems arise in entering
programs and getting them to work because
the correct number of spaces in the PRINT
statements is not always clear. When we
receive a program done on a typewriter
or a printer, we can usually figure out the
number by counting the letters in the line
above or below since each letter takes up
the same amount of space. However, this
is not always accurate because typo-
graphical errors can occur even in leaving
spaces. Another problem comes up when
we typeset programs. On the type setting
machine letters vary in the amount of
space they take up in the line and the
spaces also vary in order to make the
right hand margins even. So counting does
not work. We have tried to handle this
problem up to this point by indicating the
number of spaces in a side note. Beginning
with our next issue, we will be using a
symbol to indicate spaces where these
affect the running of the program.
If you are submitting a manuscript, we
are asking you to indicate all spaces in
the PRINT statements except the obvious
ones between words by using the symbol
7. We have chosen this because it is found
on almost all typewriters, and it is not
used on the ZX80 family of computers.
We will use a different symbol in $YNC
articles, but, even if we slip up, # will not
cause any programming errors since it
cannot be entered.
If in running a program you are sure
that you have entered it correctly but it
still does not work, check the number of
spaces in any PRINT statements. You
might experiment by changing these.
MicroAce II????
Contrary to some reports, MicroAce
is not planning at the present time to
offer a MicroAce II. When the present
stock of kits is exhausted, the MicroAce
computer will no longer be available from
MicroAce. The company goal will be to
offer equipment to upgrade the machines
already sold. An 8K ROM and a flicker
free video board (which requires 8K ROM)
will be available by the time you receive
this issue of SYNC. The RAM capacity
will be expandable by two options: a 4K
RAM and a 16K RAM. These are planned
for the fall.
SYNC Subscribers Pass the 6000 Mark
At the end of June our subscription list
totaled 6135 subscribers with 1532 outside
the U.S. California leads the list with 13%
of the total, followed by New York with
7%, and then by Illinois, Texas, and Massa-
chusetts with about 4% each. Outside the
U.S. the United Kingdom leads the list.
А P.S. from Alger Salt
Readers of Alger Salt's “А Parallel
Interface for the ZX80/MicroAce" should
note the following P.S. which arrived after
our layout was completed:
After reading the article "The ZX80
Keyboard" in the May/June issue of
SYNC I learned that the keyboard is an
input device that is addressed by any
even address. This accounts for the diffi-
culty I encountered when trying to read
from port A on the PIO. The problem
can be avoided by using address line A2
instead of А0 to select the А or B port.
That is, connect the A/B SEL line on the
РІО to a different address line than AO.
Then use only odd addresses when
addressing the PIO, i.e., addresses with
AQ = 1.
letters ООО
Gauntlet and USR(47)
Dear Editor:
My Gauntlet program in your May/
June issue can be greatly improved by
using the technique described on page 6
of the same issue. On that page, Hasse
Taube says that USR(47) will return the
end of variables address. But the end of
variables is right next to the start of the
display file. That makes my machine
language routine unnecessary.
The machine language routine made
entering the program difficult and listing
the program dangerous. But if you change
line 900 to: 900 LET D=USR(47)+2, then
you can ignore the subroutine loader and
decimal listing and also delete line 1.
This is another example of how SYNC
helps get the most out of the ZX-80. My
thanks to Michael Kirkland, Hasse Taube
and, of course, to SYNC.
Ken Berggren
104 Ridgeway Ave.
Louisville, KY 40207
Widgeteconomics
Dear Editor:
. . . I greatly enjoy your magazine;
however, I have found a few problems. In
running the Widget program I have never
been able to even break even. It is a
challenge just to keep from going bankrupt.
Is the program listing just advertisement?
Another thing I would like to see in
your future articles is how to convert
either mechanically or through a machine
code subroutine the screen to active instead
of going blank during runs.
Richard McDaniel
PO Box 71
Glasgow, VA 24555
Ed. —A number of readers of Widget
have found it quite challenging. See Reader
Васоп 5 letter below. It seems that to
remain solvent and become a successful
capitalist, you must make some minor
program changes.
Гйе conversion you ask for would cost
more than the original computer, according
to our sources. So it does not seem practical
at this point.
4
Dear Editor:
... Widget - NEAT PROGRAM! No
mistakes, but it is impossible (mathemati-
cally) to ever progress from those starting
conditions. You can only minimize your
losses to last as long as possible before
bankruptcy overtakes you. The game is a
good challenge if you start with two plants
(or other assets like inventory)...
Game of Life. You printed a program
from Thirty Programs for the Sinclair ZX80
ІК. The book Addendum Page makes
corrections in lines 450 and 460 (See
Glitchoidz Report). However, even with
these corrections the program does not
follow the logic rules although it does
run. To change the program so it follows
the rules make the following corrections:
320 IF ((1+1/7) AND 7)=0 THEN GO
TO 350
340 IF ((1-1+(1-1)/7) AND 7)=0 THEN
GO TO 360
360 FOR J=6 TO 8
400 IF (J*R=-8 OR J*R=6) AND ((1-1+
([-1)/7) AND 7)=0 THEN GO TO
420
405 IF (J*R=8 OR J*R=-6) AND ((1+1
/7) AND 7)=0 THEN GO TO 420
If you do this and the publisher's changes
in 450 and 460, the program will follow
the rules in the article.
Walter W. Bacon
RR 7, Box 68
Hopewell Junction, NY 12533
Ed.— For those who cannot abide by
the decisions of the free market place
and face bankruptcy fearlessly, a bit of
Widgeteconomics can be performed by
tinkering with the program to improve
the market position. According to my
program advisers, increase P in line 10
and/or change line 640 to read LET М=М-
20*P-15. You can also try a number lower
than 15.
Artillery and Black Hole
Dear Editor:
The Artillery game depletes my 1K
of RAM after about 5 or 6 turns. After
searching through the listing for a mistake
in my typing, I came up with the following
changes:
Omit: Line 140
Change line 320 to: 320 GO SUB 150
Add: 80 DIM S(21)
The program should now work without
any difficulties.
Also, the program Black Hole by Bill
Eckel will run in 1К of RAM if the following
changes are made:
Omit 5, 14, 16, 18, 30, 32, 34, 1025, 1130 &
1140
100 LET B=S+ 1-2*(S/2) - 2*(S/6)
+4*(5/8)-3*(5/9)
110 GO SUB 980
120 LET B=S+3-2*(S/2)+(S/3)+3*
(S/4)-4*(S/5) +5*(S/6)-5*(S/7)
+2*(S/8)-5*(S/9)
130 GO SUB 980
140 LET В=5+4-6%(8/2) + 5%(8/3)-
(5/4)--5%(8/5)-6%(8/6)--7%5/7)
-2*(S/8) +2*(S/9)
150 GO SUB 980
160 LET B=0
170 IF S=5 THEN LET B=8
180 GO SUB 980
960 GO TO 25
1075 IF Ха +5)=0 THEN RETURN
Or, as David Lubar might want to write
it:
100 LET B=-2*(S=1)-(S=2)-2*(S=3)
-(S=4)-2*(S=5)-3*(S=6)-4*(S=7)
-7*(S=8)-5*(S=9)
120 LET B=-4*(S=1)-3*(S=2)-5*
(S=3)-7*(S=4)-4*(S=5)-9*(S=6)
-5*(S=7)-9*(S=8)-6*(S=9)
140 LET B=5*(S=1)-6*(S=3)-6*
(S=5)-8*(S=7)-8*(S=9)
Replace lines 160 and 170 with:
160 LET B=-8*(S=5)
Lines 100,130,150, and 180 remain as
in the first change.
As you can see, David Lubar’s article
about Boolean operations has been used
to a great extent in shortening Black
Hole.
Joe Dell'Orfanio
122 Weaver St.
Greenwich, CT 06830
SYNC Magazine
Dear Editor:
Bill Eckel’s Black Hole (SYNC 3:8) can
be compacted to fit in less than 1K of
memory, thus making it fit neatly into an
unexpanded ZX-80. The following con-
versions should work:
Changes: 20 LET X(5)— -1
44 IF X(D THEN PRINT
иж.
46 IF NOT X(I) THEN
PRINT 0;
78 | IF NOT X(S) THEN GO
TO 70
980 IFNOT X(B) THEN GO
TO 986
983 IF X(B) THEN LET
X(B)=0
986 LET X(B)= -1
1010 IF Х(І) THEN GO TO
1050
1050 IF X(5) THEN RETURN
1070 IF NOT X(I) THEN
RETURN
1100 IF NOT X(I) THEN
RETURN
1120 PRINT *YOU WIN"
I used the first conversion as it was my
own, and I hadn't yet read Mr. Lubar's
article. I have found no problems in the
playing of Black Hole after the conversion
was made. I have also found that any one
of the possible solutions is actually two
solutions... just reverse the order. Happy
Star-Shooting.
Mark Kleinman
4228-D FCN
McGuire AFB, NJ 08641
Basic Computer Games
on the ZX80
Dear Editor:
Please tell me if the programs in Basic
Computer Games and More Basic Com-
puter Games work on the Sinclair ZX80
and VIC-1001.
A. Samereu
4946 Dornal
Montreal, Quebec H3W-1W2
Canada
Ed. — These programs will not work directly
on the ZX80 for two reasons. First, they
must be translated, that is, adapted to the
specific form of Basic that the ZX80 uses.
This is not difficult after you get some
experience in programming and after you
put SYNC articles to work for you. Second,
July/August 1981
many programs even when translated will
require more than 1K RAM. So before
you enter a program, you can give it a
rough check for size by comparing it to a
1K program printed in SYNC. If you want
to be more precise, you can count the
bytes in the translated program. The line
entry requires 2 bytes; each keystroke in
the line content counts as one; the NEW-
LINE entry adds one more.
LED Fringe Benefit
Dear Editor:
I added the LEDs to monitor tape input
as described by Cecil Bridges in the initial
issue of SYNC. An additional advantage
of this modification that he did not mention
is that it eliminates the need to disconnect
the ear cable on the recorder in order to
position a tape for program loading (if
you have a tape recorder with a digital
counter). Simply advance the tape to the
appropriate number on the counter, type
LOAD, start the recorder, and when the
red light goes out type NEWLINE.
William H. Caskey
1112 Pake Lane
Morris, MN 56267
Memory Mapping
Dear Editor:
The one thing ГА really like for your
editors to address is how we get information
into the ZX80 from the outside world
using memory mapped input. I’m afraid
to use the same approach for input that I
used for output (i.e., writing to a nonexistent
ROM address) because when I PEEK(4097)
I get 64 decimal. This implies to me that
somebody is on the data bus (at least D5).
I'm afraid to put anything on the data bus
for fear of having two chips on the bus at
the same time and damaging someone.
Of course I don't have a circuit schematic
with the 7Х80 so I can't really decide
whether or not the risk exists or whether
D5 just appears high because one tristate
doesn't clamp all the way. Can you sell
me a schematic for the ZX80?
William Byrne
2 Cypress Dr.
Wichita, KS 67206
Ed. – А suggestion from David Ornstein:
Put the memory map input port in any
address between 12 and 16K.
Schematics of the ZX80 are available
at no charge from Sinclair Research
Limited, 50 Staniford St., Boston, MA
02114.
SYNC Coverage
Dear Editor:
. . . I hope that all the new products
coming out will not affect your policy of
sticking to the basic machine. Anyone
with new ROM can, I think, easily translate
old ROM programs, whilst the converse
is not always possible. I hope that you
could follow the ideas of Interface the
National ZX80 Users Club magazine over
here and produce mainly ІК programs
with an occasional 4K or more.
One thing I would like to see in SYNC
is more attention given to PEEK, POKE,
and USR. Most people can devise a
program just using Basic, but if you have
no knowledge of machine code or the Z-
80, such as Ken MacDonald's EXCEL-
LENT space intruders program advertised
p. 19 [issue 1], are unintelligible—all I
know is that they work...
I hope the 7Х80... catches on over in
the States as well as it has here; if the
example set by the TRS-80, PET and
APPLE is anything to go by then we're in
for a good deal of excellent American
software — especially from Creative Com-
puting!
Richard J. Barton
12 Mill Lane
Camblesforth,
Selby
North Yorks
ҮО8 SHW
U.K.
Ed. — While the scope of SYNC must grow
to meet the needs of our readers as they
also grow in knowledge of the machine
and expand their equipment, we will not
leave behind the people with the basic
ZX80 nor those people who are new to
computing. Again, authors take note.
PEEK, POKE, and USR are among the
most frequently requested topics for
articles.
Currently Technical Services Manager,
David Ornstein has been with Sinclair since the
opening of its U.S. office. He has been involved with
Sinclair's technical hotline, technical writing, and
machine servicing. His primary interests are in
the areas of software and hardware R & D, and
system integration.
His secondary interests are reading (Frank Herbert),
listening (Pink Floyd) and sharing
SYNCSUMs
One day, I was typing a system-check
program into our computer. I took four
and a half hours to enter the program. As
I was about to run it, an awful thought
occurred to me: What if I had made an
error in my typing? Since the program
had access to all parts of the system, a
typo could be fatal. I decided to check it
against the listing . .. once. Then I ran it.
The end result— that I overwrote the sys-
tem disk—is irrelevant. But what is
important is this: /f the program listing
had included the program's SYNCSUM, |
would have known better.
What is a SYNCSUM? A SYNCSUM is
what is known as a checksum, or, rather,
a modified version of a checksum. The
checksum is a method of checking to see
whether a program has been entered cor-
rectly by letting the computer add up all
the bytes in a program. To use this error-
checking method, you simply compare
the checksum of the original program
with the checksum of the program you
have entered. If the numbers are not the
same, you have made an error in entering
the program. If the numbers are the
same, the chances are about 90% that
you have entered the program correctly.
In the ZX80, a certain area of memory
is used to hold the current program. This
area begins where the area for system
variables ends. For the 4К ROM, this
address is 16424 decimal (4028 hex); for
the 8К ROM, 16509 decimal (407D hex).
А system variable points to the first byte
after the program area. The 4K and 8K
ROMs format memory differently. In a
4K system, therefore, this variable is
VARS (which points to the first byte of
the VARiable Storage area), but in an 8K
system, it is D-FILE (which points to the
first byte in the Display FILE). These
variables are stored at locations 16392
(4K) and 16396 (8K), respectively.
6
ПпЕГГЕрІГІ о
David Ornstein
The assembly language program,
shown in listing 1, is used to generate the
current program’s SYNCSUM on a 4K
system. The corresponding program for
an 8K system is shown in listing 2. You
will notice that it is not adding all the
bytes, but XORing them together. This is
the modification of the standard check-
sum method referred to earlier. You will
end up with a number which is less than
256.
To use the SYNCSUM program on a
Basic program requires that the SYNC-
SUM program be resident (i.e., in mem-
ory) all the time. This can be accom-
plished first, by reserving some memory
(RAM) such that Basic will not tamper
with it, and, second, by loading the
SYNCSUM routine into this area. List-
ings 3 and 5 are programs to reserve the
required amount of memory, 27 bytes.
They should be used on 8K and 4K sys-
tems respectively. Listings 4 and 6 are
programs to load the machine language
SYNCSUM generation program into this
previously reserved memory space.
These programs should be run at the
beginning of any session of computer use
when you may want to know a programs's
SYNCSUM. From the time they are run
until the computer is turned off, obtain-
ing the SYNCSUM 15 simple: type
Label Hex Assembly Code Comments
4KSSUM: 212840 LD HL,16424 ;HL-Start
ED5B0840 LD DE,(VARS) ;DE=Stop
0600 LD B,00 “В--00 (Result Accumulator)
LOOP: 7С LD A,H И HL=DE then XORNXT
BA СРО
2008 ІК NZ,XORNXT
7D LD A,L
BB CPE
2004 JR NZ,XORNXT
DONE; ;else done
68 LD L,B slow byte returned is SY NCSUM
2600 LD H,00 shigh byte is 00
C9 RET
XORNXT: ХОК the next byte into the
;Result Accumulator.
78 LD A,B "бес current RA
AE XOR (HL) "ХОК it in
47 LD B,A ;put back result into RA
23 INC HL ;bump pointer
18ЕЕ JR LOOP ‚ро back for next byte
Listing 1.
SYNC Magazine
PRINT USR(x), where x = your memory
size (for example, 1024, 2048, 16384) - 27
+ 16384, followed by NEWLINE as always.
Thus x will equal 17381 for 1K, 18405 for
2K, and 32741 for 16K.
Enter (or LOAD) the RSV program
(listing 3 or 5) and then RUN and NEW-
LINE. The 4K program will prompt you
for MEMORY SIZE?" Enter your memory
size (1024, 2048, 16384) and NEWLINE.
Next enter (or on 8K systems only, LOAD)
the LDR program (listing 4 or 6). On a 4K
system LOADing the LDR program after
using RSV will cancel the effects of running
the RSV program.
Press RUN and NEWLINE. Again the
4K program will prompt you for “МЕМ-
ORY SIZE?" Again enter it and NEWLINE.
The 4K "MEMORY SIZE?" prompt will
return to the screen, but hit NEWLINE
and you will return to program mode.
The SYNCSUM routine is now resident.
On an 8K system, type NEW and NEW-
LINE. On 4K systems, as noted earlier,
using the NEW command will delete the
SYNCSUM routine from memory. There-
fore, to clear out the 4К LDR program,
you must delete each line individually.
To delete, e.g., line 10, type 10 and
NEWLINE. Repeat until the whole program
is gone.
You can now begin entering your pro-
gram. Once again, if you have an 8K
system, you can LOAD your program.
With 4K you must type in each line
individually, as LOADing will destroy the
SYNCSUM routine. You can now obtain
the SYNCSUM at any point along the
way via the PRINT USR (x) command
(see above for the size of x). When you
have finished and you are sure your
program is correct, call for the SYNCSUM
for the entire program. Write it down at
Label Hex Assembly Code Comments
8KSSUM: 217040 LD HL,16509 ;HL=Start
ED5B1240 LDDE,(D-FILE) ;DE-Stop
0600 LD B,00 ;В=00 (Result Accumulator)
LOOP: ТС LD AH ЈЕ HLADE then XORNXT
BA CP D
2008 JR NZ,XORNXT
7D LD A.L
BB CPE
2004 JR NZ,XORNXT
DONE: ;else done
68 LD C,B slow byte returned is SYNCSUM
0600 LD B,00 shigh byte is 00
C9 RET
XORNXT: ;XOR the next byte into the
;Result Accumulator.
78 LD A,B ‘Get current RA
AE XOR (HL) ‚ХОК it in
47 LD B,A ;put back result into RA
23 INCHL ;bump pointer
18ЕЕ JR LOOP ;go back for next byte
Listing 2.
end of your program for future reference.
Be sure to include it after the end of any
programs submitted to SYNC.
This method will also work just as well
with the ZX81 since it uses the SK ROM.
I hope this idea is as helpful to ZX80
owners as it is to the rest of the computer
world.
Until next issue, same relativistic time
period, same non-euclidian universe. "g
5 LET R=27
10 PRINT "MEMORY SIZE ?"
20 INPUT M
30 LET M=M-R+16384
35 POKE 16999, 33
40 РОКЕ 17000,М
50 РОКЕ 17001,М/256
60 РОКЕ 17002,195
10 LET R=27 [the number of bytes to reserve] 70 POKE 17003,107
20 LET КАМТОР=РЕЕК (16388) +РЕЕК (16389)*256-В. 80 POKE 17004,2
30 POKE 16388, ВАМТОР-256*ТМТ (RAMTOP/256) 90 LET K=USR(16999)
40 POKE 16389, INT (RAMTOP/256)
50 NEW
Listing 5: 4K ROM RSV
Listing 3: 8K ROM RSV.
10 КЕМ 212840ED5B084006007CBA20087DBB
2004682600C978AE472318EE
15 LET В=27
10 REM 217040ED5B124006007CBA20087DBB 20 PRINT "MEMORY SIZE ?"
2004680600C978AE472318EE 30 INPUT M
20 LET ВТ=РЕЕК (16388)+PEEK (16389) 256 40 LET RT=M-R+16384
30 FOR В=0 TO 26 50 FOR B-0 TO 26
40 LET Х= ( (РЕЕК (16509+5+8В*2)-28)*16+(РЕЕК 60 LET X-((PEEK(1642443-B*2)-28)*16--(PEEK
(16509--5--В%2-1)-28))
50 РОКЕ ВТ+В,Х
60 МЕХТ В
Listing 4: 8K ROM LDR
July/August 1981
(16424+3+В*2+1)-28))
70 POKE ВТ+В,Х
80 МЕХТ В
Listing 6: 4K КОМ LDR
Machine Code Keyboard Scanning Program
Visions danced in my head! Visions of
a completely controlled Amateur Radio
station.
Imagine! A microprocessor-controlled
system that would translate a Morse Code
message and display it on the monitor,
translate a message into Morse Code and
transmit it at a pre-determined code speed,
control a rotor to allow a beam to follow
the Oscar satellites (satellites developed
by an international Amateur Radio group
for its exclusive use), and automatically
log all the stations that I had communica-
tion with. The possibilities are endless.
I explained to my wife that a personal
computer could do more than play games.
(How else was I to persuade her that a
computer was a necessary purchase?) 1
listed all the useful functions. At first she
listened to my pipedreams in disbelief,
but as my plans grew more detailed and I
gave rational explanations of how my ideas
could be accomplished, she became inter-
ested, then impressed.
My immediate interest in a computer
was to develop a Morse Code transmit-
receive converter. Then, when more
memory became available, it would grow
into the self-contained control system I
had always envisioned.
My MicroAce 2K kit arrived, and it
took less than a week to assemble. Finally
I was ready to program a task. But wait, a
good functional check of the system was
in order. Why not program a few games?
Bombardment is fun, and Depth Charge
adds even more challenge. The new issue
of SYNC contains an enjoyable behind
the Castle Doors game, and I have got to
try the “Draw a Picture” program. Two
months later enough games had been
played on the system to functionally check
an IBM 370.
“Okay,” My wife said. “You were right.
Personal computers are useful. I mean, if
you're ever stuck in a dungeon, at least
you'd know which door to choose."
I chuckled at this but realized she had
a point. Computer games can be a trap.
Bernard Puerzer. 3209 So. Kinnickinnic Ave..
Milwaukee. WI 53207.
8
My initial project was being ignored. It
was time I got busy.
I felt that the Morse Code transmitter
portion of my project would be the easiest
since I would need additional circuitry if
I wanted to receive Morse Code and
translate it. The computer, as it stands, is
not equipped to convert the output from
the receiver into a digital waveform. Due
to obvious memory constraints, the pro-
gram has to be done in machine code. My
plan was to read the keyboard input, find
the input by consulting a look-up table,
then convert it to a Morse Code type
digital output which would clock a relay
(on the transmitter). A software keyboard
buffer is needed to allow the operation to
‘type ahead’ of the transmitted output,
and a driver subroutine is needed to clock
the relay at the desired code speed. The
typed input should also be displayed on
the monitor. This can be accomplished
within the MicroAce 2K memory if the
code is written properly.
The first stumbling block came when I
tried to read the keyboard input, using
machine language code.
The Problem
To read the input in Basic, an input
statement is used, but the INPUT command
looks for either a number or a letter and
cannot be used to accept both randomly.
I could not use it for my application, and
other programs may have a similar problem.
To read a key on the keyboard using one
Basic routine would use up too much
memory, and I doubt that it is even possible.
Therefore, it is machine code all the way!
Even a person with no interest in Morse
Code could find the keyboard input routine
interesting since it has many other appli-
cations. If nothing else, it provides a better
understanding of the Sinclair/MicroAce
hardware.
The Solution
I began by studying the schematic to
understand how the keyboard is read by
the software. As it turns out, both the
Sinclair and MicroAce use the same
technique. The keys are wired in a matrix
Bernard Puerzer
configuration, and the rows of the matrix
are connected to the Z-80 address lines
А8-А15, while the columns are connected
to the Z-80 through a latch that is energized
by the KEYBD signal (active whenever
an I/O instruction is executed). When a
key is depressed, the address line for the
row of the key and the data line for the
column of the key are connected. If the
address line is low at that instant, the data
line will be pulled low. Therefore, the Z-
80 will analyze the data lines after a known
address is issued with an I/O instruction
to determine if a specific key was
depressed.
If all the address lines A8-A15 were
low, the Z-80 could not tell which row
caused the data lines to change. So to
scan the keyboard, each I/O instruction
must have only one address line low at a
time to determine the exact key that was
depressed.
The Machine Code Monitor
Understanding the technique, I pro-
ceeded to write the machine code to
decode the keyboard. Although I tried to
keep the code as efficient as possible, it is
still almost 100 bytes of instructions. Typing
in this many POKEs did not seem much
of a challenge so I wrote the following
program in Basic:
5 LET MARK=0
10 PRINT “ENTER STARTING
ADDRESS”
20 INPUT A
30 PRINT А; “ (1 sp.) "; PEEK (A)
40 INPUT B
60IFB 255 THEN GO TO 130
70 POKE A,B
80 PRINT A; “ (1 sp.) ”; PEEK (A)
90 LET MARK=MARK +1
100 IF MARK 10 THEN GO TO 110
105 CLS
107 LET MARK = 0
109 PRINT А; “ (1 sp.) ”; PEEK (A)
110 LET A = А+1
120 GO TO 30
130 STOP
Figure 1.
SYNC Magazine
This program allows easy loading of
sequential memory locations. When it
begins, it asks for the starting address,
entered in decimal. The program then
displays the address and its current memory
contents.
Enter the new contents in decimal,
followed by a return. The program displays
the new contents and then automatically
increments to the next location, displaying
the address and current contents. Continue
entering your machine code program.
When that is completed, enter a number
larger than 225 to stop the monitor
program.
I am sure you will find this method
much easier to use than entering a POKE
instruction for every machine code instruc-
tion to be loaded. Since so much machine
code is written in hexidecimal notations
іп the ‘real world, a good modification to
this monitor would be to allow the memory
contents to be loaded by entering the
number in hex notation. Since this would
require entering the numbers (0-9) and
letters (A-F), a keyboard input program
such as the one to be described would be
required. Now that we have an easy way
to enter machine code on our Sinclair/
MicroAce the rest is a piece of cake.
TZ
CRAPS
July/August 1981
BET THE PASS LINE (WITH ODDS), HARDWAYS, THE FIELD,
BIG 6 & 8, ETC., (WITH RULES). USES LAS VEGAS ODDS.
BLACKJACK
USES FOUR DECKS. SHUFFLES AUTOMATICALLY. PLAY
AGAINST THE DEALER. BLACKJACK WINS 17-1. GRUB-
STAKE KEY WHEN YOU GO BROKE!
NOW MG BSS
Dg GA REAR,
I have not yet devised a clean way of
saving long machine code programs on a
cassette tape, but I did find a technique
that works. If you set up a few DIM
statements in the beginning of the monitor
program to dimension a few arrays with
variables not used in the program, the
system will ‘reserve’ memory locations for
these arrays. The machine code can now
be loaded, and, when the SAVE command
is executed, the Basic program, including
the arrays, will be saved. With some luck,
the machine code program will reside in
the ‘reserved’ space and be saved. When
the program is downloaded from tape and
re-run, be sure to use the GO TO and not
the RUN instruction to begin the program,
or the array space will be erased.
Keyboard Input Program
The program, as written, resides in
memory locations 17401-17497. If this is
not convenient on your system, the pro-
gram can be re-located easily enough by
changing a few of the instructions that
reference memory.
When the program is run, the code of
the depressed key is placed in memory
location 17400. Therefore, a PRINT CHR$
(PEEK(17400)) command will display the
key depressed on the keyboard. Other
uses of this code can be devised.
As the program is being executed, it
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will loop between addresses 17405-17412
until a key is depressed. The INA,(C)
instruction will place the contents of the
B Register onto the address lines A8-A15
and the contents of the C Register onto
address lines A0-A7. Therefore, by rotating
a zero through the B Register and keeping
the C Register set to zero, the keyboard
can be scanned. When the data lines
change, we know a key was depressed.
Now we must decode the findings.
When a key is depressed, the accumu-
lator and the B Register are analyzed to
determine which key was depressed. Figure
2 shows the A and B Register contents for
each key.
Accumulator Contents
30 29 27 23
[e
Сл
254
23.3
251
247
239
223
191
V
G
T
5
6
У
Н
Register В Contents
line
127 | space œ M N
UJ
Figure 2.
f
d
~
wh
9.95
МО POSTAGE.
NO HANDLING.
NO SALES TAX.
Тһе program now checks each bit of
the accumulator to determine which one
is low. Register C is incremented once for
each bit tested. Then each bit of Register
B is checked to determine the one that is
low. Register C is incremented by five for
each bit tested.
The contents of Register C are then
used as an offset for the look-up table
found at addresses 17458-17497. The look-
up table value is placed in location 17400
and the subroutine returns to the program
that called it.
It should be noted that this program
case.’ Code could be added to look for
the SHIFT key code. If detected, the
program could then add an offset to
Register C and jump back to look for
another key to be depressed. The look-up
table must then be expanded to include
all the SHIFT characters.
Conclusion
Although the code may be difficult to
follow at first, the program is really doing
a lot in 97 bytes of memory.
By the way, this program is fast! If you
use it as a subroutine in a Basic program,
the USR instructions, or the keyboard
input program will decode the NEWLINE
key that you depress after the RUN
instruction — unless, of course, you release
it in a matter of milliseconds. A good
trick is to include a FOR loop of about 10
just before the USR call instruction to
give you enough time to release the
NEWLINE key.
Now that I can read the keyboard, it is
just a small matter of time before hitting
the ham bands. But first, maybe I had
better functionally check the system by
running a few quick games of Acey
reads the total keyboard but only ‘lower- be sure enough Basic instructions precede — Ducey. a"
17449 45 55 low
А 17450 68 104 high
Keyboard Scanning Program 17451 221 335 LD A.(IX--d)
Address Decimal Octal Comments 17452 126 176 d
17453 x X don't care
17401 14 16 LD C,0 17454 50 062 LD 17400, A
17402 0 0 17455 248 370 low order
17403 6 6 LDB, 254 17457 201 311 high order
17404 254 376
17405 203 313 RLC B 17456 67 103 high order
17406 0 0 17457 201 311 RET
17407 237 355 INA, (с) 17458 1 table starts
17408 120 170 17459 63
17409 254 376 CP A, 31 17460 61
17410 M 17461 40
17411 40 50 JR Z, 17462 59
17412 248 370 (-8) 28 compliment 17463 38
17413 221 345 LD IX, Table addr -6(17452) 17464 56
17414 33 41 17465 41
17415 44 54 17466 43
17416 68 104 17467 44
17417 95 137 LD E,A 17468 54
17418 0 0 МОР |For future 17469 60
17419 0 0 МОР. | reference 17470 42
17420 14 16 LDC,1 17471 55
17421 1 1 17472 27
17422 22 26 LD DO 17473 29
17423 0 0 17474 30
17424 62 76 LDA, 00111011 17475 31
17425 59 73 17476 32
17426 198 306 ADD A,000010000 17476 32
17427 8 10 17477 33
17428 50 62 LD(17437),A 17478 28
17429 29 35 low 17479 37
17430 68 104 high 17480 36
17431 103 147 LD НА H is holder 17481 35
17432 122 172 LDA,D 17482 34
17433 129 201 ADDA,C 17483 33
17434 87 127 LD D. A 17484 52
17435 124 174 LDA.H 17485 46
17436 203 313 BITE 17486 58
17437 X X Don't care 17487 62
17438 & 040 JR NZ, cont. 17488 231
17439 242 362 -14 17489 49
17440 88 130 LD E,B 17490 48
17441 203 313 BIT C,2 17491 47
17442 81 121 Test for a five 17492 45
17443 14 016 LDC,5 17493 0
17444 5 5 17494 155
17445 40 050 JRZ, back 17495 50
17446 233 351 - 17496 51
17447 122 172 LDA D 17497 39
17448 50 062 LD(17453),A End of Program.
SYNC Magazine
The TLS Function
Rolf L. Miller
Do not overlook the use of the TL$ function when you are
creating programs. It is a very useful item. This function
allows the 7Х80 user to process a string in much the same
way that other computers READ DATA statements.
To see how it works in this fashion, consider first the
CODK(string) function. It will “read” and give the code of the
first character ina string. Thus, if A$=“ABC”, CODE(AS)
would result in 38, the code for A.
Now add the TL$ function: LET A$=TL&(A$). Тһе TL$
function strips the first character from the string—A in this
case — leaving “BC” in A$. If CODE(AS) is now reintroduced,
it will “read” B and give its code, 39.
Clearly, an entire string can be “read” in this way. So, for
example, say you have a stock portfolio of five stocks, namely:
100 shares of ABC, 200 of XYZ, 300 Q, 200 KLMN, and 100
ZX. The following program will print the number of shares in
100s, the stock symbol, ask for the last (current) price per 100
shares (stock prices are quoted per share so that 5 1/4 would
be input as 525), and, then, after all five stocks have been
processed, print the total value of the portfolio.
Rolf L. Miller, 492 S. Anacapa, Ventura, CA 93001.
as
қ Қ E e.
ЖТ yh
Ti Co S
“It’s a new game called ‘Artillery’! Pretty Realistic, Huh... ?"
July/August 1981
10 LET У=0
20 LET P$=“.1 АВС.2 XYZ.3 Q.2 KLMN.1 ZX.”
30 IF CODE(P$)=27 THEN LET P=CODE(TLS§(P$))-28
40 PRINT CHR$(CODE(P$));
50 LET P$=TLS$(P$)
60 IF P$=“” THEN GOTO 130
70 IF NOT CODE(P$)=27 THEN GOTO 40
80 PRINT, * INPUT LAST PER 100”
90 INPUT L —use 100 for test RUN
100 LET V=V+(L*P)
110 CLS
120 GOTO 30
130 CLS
140 PRINT “PORTFOLIO VALUE= ”;V —test RUN should
give 900
In line 20 it is noted that the code for . is 27 and acts as a
flag to control the loop routine following.
In line 30, subtracting 28 from the code for 1, 2, 3, etc.
results in 1, 2, 3, etc. since the code for 1 is 29, for 2 is 30, etc.
and thus sets P at the proper value. Note here that the TL$
function is used to “look” one character ahead in the string
without actually stripping the string.
To see the value of the TL$ function here, try writing a
program without using TL$ to accomplish the same results as
this program and look at the length and memory difference.
Another example of using TL$ is seen in this version of
Mastermind. Further applications will be left to your imagina-
tion. |
Mastermind
Э КЕМ COFYRIGHT 1981 BY ROLF L.
10 LEX Х=15
20 LET A=9999+RND (22768)
ЗО LET A$=STRE (A)
40 LET Вф=аф
ЗО IF Хо THEN GOTO 190
60 LET XzX-1
70 LET 2-0
80 PRINT "5 NO.GUESS ":
90 INFUT 6%
100 IF 6%=A% THEN GOTO 220
110 РКІМТ (5%;
120 IF BH$-"" THEN GOTO 170
150 IF CODE (G$)=CODE (HRS) THEN LET 77-1
140 LET G$-TL$t(G3$)
150 LET Bt=TL (Bs)
160 GOTO 120
170 PRINT "
180 GOTO 40
190 FRINT
MILLER
"22. RIGHT ВХ (2 әр.)
200 PRINT "YOU LOSE THE NO. WAS "A$
210 STOF
220 PRINT
250 FRINT „A$
240 PRINT
20 PRINT “YOU WIN"
Frogram Notes:
110 displays number guessed.
170 displays number of digits
in proper place of sequence
and number of turns left
in i bh,
11
A Subroutine for Serial Data Output
Trying to write machine code sub-
routines for my ZX80 presented some
problems. This article details the problems
with their solutions, and shows a simple
subroutine to output data serially by bit
to an asynchronous peripheral.
The first problem was to find a space in
RAM to write my subroutine. The obvious
space was the SPARE area shown in
appendix П of the ZX80 Manual (See
Figure 1). It is easy to find the start of the
spare area by PEEKing into locations 16400
and 16401 which point to the display file
end "DF-END" (ZX80 Manual, appendix
III). But the problem is that the SPARE
area is sandwiched between two dynamic
areas. The VARIABLES, WKG SPACE,
and DISPLAY FILE may expand pushing
DF-END closer to the top of stack and
overwriting my routine. The stack itself
may get bigger and overwrites the
routine.
A second problem came up when I
tried to save the program on cassette. My
machine code subroutine was not saved
simply because the SAVE statement causes
the ZX80 to save on cassette from the
start of RAM up to E-LINE only (Figure
1).
A technique around these problems was
to include my subroutine in a REMark
statement and thus allocate a fixed area
of RAM for it. I was able to save it on
cassette, too.
5. Onsy, Р.О. Box 2952 SAFAT, Kuwait, State of
Kuwait, Arabian Gulf.
12
S. Onsy
ee aaaaaaaaaamamamaħÃă
SYS VARS
RMBOT
PROGRAM
VARS
VARIABLES
E-LINE
WKG SPACE
D-FILE
DISPLAY FILE
DF-END
SPARE
SP
STACK
Figure 1. ZX80 Memory Map.
I used the following procedure to input
the subroutine:
1. Calculate the length, in bytes, of the
subroutine.
2. Enter a REM statement at line 1.
Line 1 is used to insure that the REM
statement will always be the first one in
the program and that it will have a fixed
address in RAM. Using numerics helped
counting the number of reserved bytes.
The REM statement appeared as follows:
0001 REM 012345678901234567890123456
7890 etc.
3. Enter the subroutine starting at address
16428.
Restrictions
While writing the subroutine I noticed
the following:
1. Never use the code/data of 76 hex
since it is an end of statement to the
ZX80. OP code 76 hex is not used anyway
since it is a HALT command to the Z-80
microprocessor.
2. Since codes 40 to 7F hex cause
problems with the ZX80 LIST command
if they are included in the REM statement,
I avoided displaying the REM statement.
This was achieved by adding dummy
statements until it disappeared from the
screen and then deleting the dummy state-
ments.
Applications
The listed Z-80 subroutine was used to
output data asynchronously to a serial
printer at 300 baud. The output was taken
from IC-11 pin 11 (Figure 2). The signal is
at TTL level, and therefore the interface
circuitry in the printer was bypassed (Figure
3). The baud rate can be changed by
simply changing the bit time loop.
SYNC Magazine
Figure 2. Serial O/P from IC11.
From ZX80 ІСІ1-11
I/P 239 Po |
pees 1488 (typical)
or CCITT
Figure 3. Typical I/F circuit.
The Basic program shown uses the above
subroutine to LIST itself on the printer
from the PROGRAM area in RAM. The
program is slow and not practical to use.
However, it demonstrates some techniques
for the ZX80. I have included enough
REMarks to make the program self-
explanatory. Since the program uses a
flow similar to the ZX80 LIST command,
it will be practical and much faster if the
program is rewritten in the Z-80 code
making use of the ROM subroutines. In
the following discussion all addresses,
codes, and data are in hex. The registers
mentioned are the Z-80 internal registers.
The heart of the ZX80 LIST statement
is a call to 04F7 which edits statement
lines from the PROGRAM area in RAM
into the display file. Register HL’ points
at the statement being edited while the
resulting statement is stored at the location
pointed at by DF-END. The 04Е7 sub-
routine further calls two subroutines:
ОӨВЕ: ‘Translates statement numbers
from binary to decimal ех-
pressed in the ZX80.
Changes the commands and
operators (i.e., codes > D3) to
their proper mnemonics.
0684:
July/August 1981
The following flow chart shows how a
printer LIST routine that uses the ROM
subroutines may look:
ENTRY
Preset Z-80 registers.
Check BREAK key.
BREAK?
CALL O6BF: Get
statement number.
Next character falls
between 40 and 7F?
Character >CO
CALL 0584: Get
mnemonics.
CALL 0559: Store
character.
Translate statement from
ZX80 code to ASCII and
print.
N
P End of Program area?
Y
O! O3
a-— EXIT
NEW ENGLAND
SOFTWARE
7 GAMES FOR THE ZX80
AND MICROACE ON CASSETTE
MASTERMIND
DOUBLEMIND
SLOT MACHINE
CRAPS
TIC TAC TOE
SUB RESCUE
WHITE HOT NUMBER
ALL RUN IN 1K RAM
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Box 691
Hyannis, MA. 02601
Е
£ 6.00 Irs ass (U.0.A.
Air Mail (England)
YOUR BEST VALUE IN
QUALITY SOFTWARE
Are you in
SYNC?
If not, you should be. We would like any
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grams, games or tips which you have to
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lively if accompained by photos (black
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you do not have an output printer, please
type program listings and carefully check
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Sample runs should be included with pro-
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13
Output Subroutine
This is a subroutine to output one byte
serially by setting and resetting a latch in
the 7Х80. Тһе data is preceded by a start
and followed by a stop bit. The subroutine
expects the byte to be at (DF-END)+2.
All addresses, codes, and data are in
hex. |
Can a computer mow your lawn? Not yet.
But a flowchart can show you how to
make money cutting five lawns a day. The
flowchart is easy. Mowing the lawns is still
hard work.
Dr. Sylvia Charp and Marion Ball wanted
a way to introduce basic computer concepts
to children in grades 5 to 9 of the Philadelphia
City Schools. So they identified some tasks
that kids understood like mowing lawns,
issuing paychecks and controlling traffic
lights. They showed how computers are used
in these tasks.
14
LABEL
SPACE
NZ,LOOP
OPERAND
ADR
CHRCTR РОЗН HL SAVEHL 402C Е5
LD H,IY-c*11) GET ADDRESS ОЕ 402D FD 6611
LD Г.(ТҮ--10) DF-END AND 4030 FD 6E 10
INC HL INCREMENT 4033 23
INC HL TWICE 4034 23
BR (HL) GET NEXT BIT 4035 СВІЕ
POP (HL) RESTORE HL 4037 El
DJNZ BITTEST IF NOT LAST BIT 4038 100C
GO TEST IT
STOPBIT ІМ A,(FE) OTHERWISE OUT 403A DB FE
JR BITTIME A STOP BIT AND 403C 1811
RETURN
ENTRY LD HL,402C INITIALIZE HL 403E 21 2C ЗЕ 24
SCF AND PREPARE FOR 4042 0609
CCF START BIT 4044 37
BITTEST PUSH HL SET RET ADDRESS 4045 35
JR NC,SPACE IF ZERO SPACE 4046 3004
MARK IN A,FE OTHERWISE MARK 4048 DB FE
BITTIME LD D,80 START ОҒ ОМЕ ВІТ 404Е 1680
LD E,F6 TIME LOOP 4050 IE FD
LOOP INC D 4052 14
JR NZ,LOOP 4053 20FD
INC Б 4055 IC
Computer
ря лене
Flowcharts - A basic concept
They devised flowcharts. They located
scores of photos. And they found an artistic
high school student to illustrate these con-
cepts with lively full-color drawings.
They then wrote a light-hearted but infor-
mative text to tie it all together. It talked
about kinds of computers, what goes on
inside the machine, the language of the
computer and howcomputers work for us.
They took the problem of averaging class
grades and showed how a simple yrogram
could be written to do this job.
Well-qualified authors
Marion Ball has written other books on
computer literacy. Sylvia Charp is the director
of educational compuuting for Philadelphia
City Schools. They pooled their talents to
produce this book, Be AComputer Literate.
This easy-to-read book explains how com-
puters are used in medicine, law enforce-
ment, art, business, transportation and ed-
ucation. It's interesting and understand-
able.
Too much demand
The Bell System distributed 50,000 copies
to schools throughout the U.S. but they
couldn't meet the continuing demand. So
Creative Computing Press now distributes
the book. It's just $3.95 plus $1.00 shipping
and handling. Send name and address plus
payment or credit card number and expiration
date to Creative Computing Press, Morris
Plains, NJ 07950. Visa, MasterCard and
American Express orders may also be called
in toll-free to 800-631-8112 (in NJ 201-540-
0445).
Order yours today. If, after reading it, you
do not feel that you are "computer literate,”
return it for a full refund plus your postage
to send it back.
creative
competing
Morris Plains, NJ 07950
Toll-free 800-631-8112
(In NJ 201-540-0445)
SYNC Magazine
Program Listing
0001 REM < CLEAR ) CLEAR (7742 ОК (МОТ REM
М < N?-2 CLEAR *4 CLEAR 04 IF B89
535628
КК
0005 КЕМ ЖЖЖЖЖЖЖЖЖЖЖЖЖ ЖЖ ЖЖ ЖЖ ЖЖ ЖЖ ЖЖ ЖЖ ЖЖ K K K K K ЖЖЖ ХХ Ж
opio REM
0015 КЕМ
оого REM
0025 REM
0030 КЕМ
0055 REM
0040 REM
0045 REM
0050 REM
0055 КЕМ
OAD REM
0063 REM
0070 REM
0075 REM
HOBO REM
END+2. THE OUTFUT ТО THE SERIAL
INTEGRATED CIRCUIT OF THE 2Х80.
GET ASCII CODES FROM 2Х80 CODES.
FOR THE COMMAND/GPERATOR CODES.
WILL ВЕ АТ TTL LEVEL АТ FIN 11 ОҒ
THE РАОБКАМ ALSO DEMONSTRATES THE
STRING VARIABLES АЗ à TRANSLATION TABLE TO Ж
THIS FROGRAM LISTS ON АМ ASCIT SERIAL
PRINTER THE PROGRAM AREA OF THE 2Х80 КАМ.
THE REM STATEMENT 0001 CONTAINS A 280
CODE ТО OUTFUT ONE CHARACTER ASYNCHRONOUSL Y x
АТ 200 BAUD. THE ENTRY POINT IS АТ
16446. THE ASCII CHARACTER SHOULD ВЕ АТ DF-X
PRINTER
pL 23
USE ОР
THE FROGRAM USES а TABLE IN THE 2Х80 ROM
USED BY THE LIST STATEMENT TO GET MNEMONICSX
Ж
*
x
ADDRESS X
Ж
Ж
Ж
Ж
Ж
Ж
Ж
0140 REM OOOO OK ROKR RK ROKK ROKK KKK KK RK KKK KKK KK KK KEK KK
0150 REM Ж
0160 REM жжжжж TRANSLATION TABLE ЖЖЖЖЖ
0170 REM Ж
0180 LET X$-"446444444444448UZCDHFEJXYWVGI"
0190 REM
0200 REM A=ADDRESS OF CHARACTER TO БЕ FRINTED.
16424
0210 LET A=16424
0220 КЕМ LA=LAST ADDRESS TO BE PRINTED. БЕТ TO VARS.
O230 LET LA=PEEK (16292) +256*FEER (16293)
0240 REM XXXX* SUBROUTINE ADDRESSES жжжжх
O250 LET CRLFz1070
о260 LET SFACE=1190
0270 LET FPRINT=1240
0280 LET XLATE=970
Q290 REM
ооо REM Xxxxx MAIN FROGRAM ЖЖЖЖХ
0510 КЕМ INITIALISE LINE COUNTER
Q320 LET LC=1
ОЗЗО REM NEW FAGE
0540 FOR 4-і TO 5
0350 GO SUB CRLF
O2Z60 NEXT J
0370 REM STATEMENT NUMBER
0580 LET SN=FEEK (A) Ж256+РЕЕЕ (А+1)
0390 GO SUB SFACE
O400 FOR Ј=1 TO 4
0410 LET T=SN/1000
O420 LET C=T+48
0430 GO SUB FRINT
0440 LET SN=(SN-TK1000) k10
0450 NEXT 4
0460 LET Я=А+1
0470 REM STATEMENT
0480 LET А=А+1
0490 (ЕТ С=ҒЕЕК (A)
0500 IF С=118 THEN GO TO 880
0510 IF С>211 THEM GO TO 610
0520 IF 05227 THEN LET C=C+20
0530 IF C557 THEN LET C=C+7
0540 IF C28 THEN GO SUB ХАТЕ
оззо GO SUB PRINT
0560 GO TO 480
0565 КЕМ
0570 КЕМ COMMANDS AND OPERATORS
05/9 КЕМ
0580 REM Fi=FLAG TO INSERT SFACE BEFORE
AND AFTER MNEMONICS.
0590 REM F2=FLAG TO DEFINE END OF ММЕМОМТС.
0600 REM В =ADDRESS OF CURRENT CHARACTER
IN MNEMONICS TABLE.
0610 LET В=186
0620 (ЕТ Е1=0
0630 LET Е2=0
0640 FOR JO ТО С- 212
0650 LET B=B+1
0660 IF РЕЕК(В)<128 THEN GO TO 650
0670 NEXT J
0680 LET B=B+1
0690 LET С=ҒЕЕК (BR)
0700 IF С“128 THEN GO TO 730
0710 LET F2=
0720 LET C=C-128
0720 IF C227 THEN GO TO 760
0740 GO SUB XLATE
0750 LET Fi=2
0760 IF Е120 THEN GO TO 790
0765 LET D=C
July/August 1981
0770
07795
0780
0790
0795
овоо
0810
овго
0850
0840
0850
OB60
0870
0880
0890
0900
0910
0920
09:30
0940
0950
0960
0970
0980
0990
1000
1010
1020
1020
1040
1050
1060
1070
1080
1090
1100
1110
1140
1150
1140
1290
1160
1170
1180
11790
1200
1210
1220
1230
1240
1200
1260
1270
1280
1290
1200
NOT RE
INITIALISED ТО
GO SUB SFACE
LET C=D
LET Fi=1
LET C=C+27k(1/F1)
IF C232 THEN LET Fi=1
60 SUR FRINT
IF F2=0 THEN GO TO 680
IF Fi-2 THEN GO TO 480
GO SUB SPACE
60 TO 480
REM END OF STATEMENT
REM
GO SUB CRLF
LET А=А+1
IF БАЗА THEN GO TO 920
STOF
IF 162951 THEN GO TO 520
GO TO 380
REM
КЕМ ЖЖЖЖЖ XLATE SUBROUTINE KKK KK
REM
LET Y$=X$
FOR J=0 TO C
LET Y$-TL$(Y$)
NEXT J
LET C=CODE (Y$)
RETURN
REM
REM ЖЖЖЖЖ CRLF SUBROUTINE KKK KK
REM
REM CC=CHARACTER COUNT
LET CC=0
LET LCO=LC+1
LET С=15
GO SUB РКІМТ
LET C=10
GO SUB РКІМТ
REM DELAY FOR CARRIAGE TO SETTLE
FOR К=1 TO 5
NEXT Е
RETURN
REM
REM ЖЖЖЖЖ SFACE SUBROUTINE KKK KK
LET C=32
REM
REM ЖЖЖЖЖ PRINT SUBROUTINE 29299:
REM
REM C-ASCII CODE FOR CHARACTER TO BE FRINTED
LET CC-CC-*1
PORE РЕЕК (16400) +256xF EEK (16401) *2,C
LET G=USR (12446)
IF 73>CC THEN GO TO 1300
GO SUB CRLF
GO TO SPACE
RETURN
15
How Is К Done?
Introduction
This article shows how a routine can
be written and entered into a Z X80 that
enables the user to SCROLL the display.
In the 4K monitor there is no facility at
all for doing other than printing to the
last line of the display, and then, when
the display is full, the program will stop
unless a CLS (clear screen) command is
used.
The 8K monitor does have a SCROLL
command, but it is limited in use as it
only enables the user to scroll the whole
display one-line-up and to print to the
bottom line again.
The routine in this article will only work
under the 4K ROM.
Objectives
My first objective was to produce a
routine that would simply scroll the display
one-line-up, when called by a USR com-
mand and allow the user to continue
printing at the end of the display. However,
a second objective soon appeared and
that was to extend the routine so that
only a predetermined part of the screen
would be scrolled, thereby enabling the
user to have a “title” area at the top of
the display that would remain un-scrolled.
The routine would require from the user
that the number of lines to be left un-
scrolled be specified, using a POKE
command, before using the USR com-
mand.
Dr. Ian S. Logan, 24 Nurses Lane, Skellingthorpe,
Lincoln LN6 OTT, England. This article is the
third in a series.
16
Screen Scrolling
Dr. І. 5. Logan
The Theory
Before writing a routine that manipulates
the contents of the display file, we must
have a clear understanding of the structure
of the display file of the ZX80. Figure 1
shows the parts of the display file as they
would be produced by running the simple
program:
10 PRINT “FIRST LINE”
20 PRINT “SECOND LINE”
Press RUN and NEWLINE.
-—— D-FILE
FIRST LINE 118
SECOND LINE 118
—
|
|
L
Figure 1.
21 end-of-line
characters
SYNC Magazine
OLD Display File
NEW Display File
«--Г-ЕПЕ -&—— D-FILE
118 118
FIRST LINE 118 FIRST LINE 118
»| SECONDLINE 118 SECOND LINE 118
(11 characters)
THIRD LINE FOURTH LINE 118
FOURTH LINE 118 FIFTH LINE 118 DF-EA
(reduced
by 11)
DF-END
does not
FIFTH LINE 118 5 reqane
DF-END updating!
Figure 2.
Note that the lines are of varying length
and that they all end in a “118” (Hex. 76)
which is the end-of-line marker.
The pointer D-FILE always points to
the first character in the display file, which
is always an end-of-line character.
The pointer DF-EA points to the start
of the “lower part of the screen,” and DF-
END points to the twenty-fifth end-of-line
marker.
It is important to realize that the pointers
DF-EA and DF-END are only given their
final values when the execution of a
program finishes. Before this time the
pointers are being changed as each char-
acter is added to the display file. Therefore
before the “end of program” routine is
executed the pointers DF-EA and DF-
END both point to the last location in the
partially completed display file.
In a scroll routine it is necessary initially
to collect the current value of D-FILE
and then look through the display file
until the point is reached that is to become
the “new” contents of D-FILE. However,
if certain lines are not to be scrolled, then
these lines must be passed over, and the
last end-of-line marker considered to be
D-FILE.
July/August 1981
The length of the line to be erased is
then found, and the scrolling is achieved
by moving the whole of the remainder of
the display file down in memory so that it
overwrites the scrolled line. There then
remain two house-keeping tasks. The value
of DF-EA and the value of the system
variable 16421, the line counter, need to
be altered. DF-EA has to be reduced by
the ‘length’ of the erased line, and the line
counter has to be incremented (one added)
to take into accunt that there is now one
less line in the display file.
Figure 2 shows the action of the scrolling
routine that has left 2 lines and then scrolled
once, deleting line 3.
Loading the Routine
The following method can be used to
enter the routine into the ZX80. The
routine is kept in a REM statement held
off the screen so do not try to list it.
Enter the following lines:
10 REM 12345678901234567890123456
78901234567890123456789012345678901
2345678901234567890
20 КЕМ *** SCROLL ***
30 REM FIRST POKE 16427 WITH
THE NUMBER OF LINES TO BE LEFT
THEN USE LET K=USR(16430)
Now push line 10 off the screen by using
EDIT.
The actual steps are:
HOME
EDIT
RUBOUT,RUBOUT, ENTER 40 and
NEWLINE.
EDIT
RUBOUT, RUBOUT, ENTER 70 and
NEWLINE.
EDIT
RUBOUT, RUBOUT, ENTER 80 and
NEWLINE.
EDIT
NEWLINE
LIST 20
and delete lines 40, 50, 60, 70 and 80.
The actual machine code can now be
POKED into line 10 by using a simple
loader.
17
The Assembly Language Listing
4028
4qQOZ2B OO
4020 OO оо
4O2E 2а ОС 40
4021 ED SB ОЕ 40
дода 22 20 40
4038 23
4059 O1 00 00
40230 SE 73
ДОЗЕ ZC
ДОЗЕ ЕВ
4040 А?
4041 ED 5
404% 20 О
4045 CF О
4047 19
4048 ЕВ
4049 ВЕ
404A 28 O4
4040 22
4040 QC
404E 18 EF
4050 За 2B 4
4055 А,
4054 28 06
4056 3D
4057 SS ӘБ 40
доза 18 D9
довС 79
4050 EB
ДОЗЕ n?
AoSF ED 52
4061 44
4062 4D
406% 2A 20 40
4066 ЕВ
4067 ED ЕО
4069 ZA ОЕ 40
4O06UC ДЕ
4060 27
4oó6E ED 42
4070 22 OE 40
407% SA 25 40
4076 2C
4077 32 да 40
407A C9
nd
LEAVE
NEW D-FILE
START
LINE END
NEXT
ERROR
NO ERROR
э COUNT
SCROLLING
ORG 4028
DEFB
DEFW
LD HL, tD-F ILE?
LD DE, (DF-EA)
LD СМЕМ D-FILE),HL
INC HL
LD ЕС, +0000
LD А, +79
ІМС а
ЕХ DE,HL
AND А
SBC HL, DE
JR NC,NO ERROR
RST 0008, "9"
ADD HL, DE
ЕХ DE, A.
ЕР (HL?)
JR Z,COUNT
INC HL.
INC С
JR | NEXT
LD A, (LEAVE)
AND A
JR SCROLLING
DEC A
LD (LEAVE) „га
JR LINE END
LD А.С
ЕХ DE,HL
AND А
SEC HL, DE
LD BH
LD C,L
LD HL, (NEW D-FILE)
EX DE,HL
LDIR
LD HL, (DF-EA)
LD C,A
SCF
SBC HL, BC
LD (DF-EA),HL
LD А, (LINE COUNT)
INC а
LD (LINE COUNT), Â
RET
No. of lines unaltered.
Line end address store.
Pick up D-FILE.
Fick up DF-EA.
Address of scroll line.
Enter next line.
Initialize counter.
Form end-of-line
marker in A register.
Change over registers.
Clear carry flag.
Find if DF-EA has
been reached.
Will give "А" error.
Reform HL.
Exchange back registers.
Look for end of line.
Yes. End of line found.
No. So go to next
character, incrementing
counter and address.
Collect the parameter.
Is it zero?
Yes. бо scroll.
No. So pass to next line.
Replace the parameter.
Back to LINE END.
Save C in A register.
Exchange registers.
Clear carry flag.
Find length of rest of
the display file and
put it in ВС.
Collect the line end
address and scroll the
display file.
Reduce the value of
DF-EA by the size of
the character count
of the scrolled line
that was saved in A.
Increment the value
of the system variable
16421- line count.
Return to Basic.
100 FOR 1=16427 to 16506
110 INPUT A
120 POKELA
130 NEXT I
The data for this routine is:
0,0,0,42,12,64,237,91,14,64,34,44,64,35,
1,0,0,62,117,60,235,167,237,82,32,2,
207,9,25,235,190,40,4,35,12,24,239,58,
43,64,167,40,6,61,50,43,64,24,217,121,
235,167,237,82,68,77,42,44,64,235,237,
176,42,14,64,79,55,237,66,34,14,64,58,
37,64,60,50,37,64,201
So enter lines 100 to 130 and RUN 100.
Enter the machine code carefully. The
checksum for the data is 6578, and this
can be checked by adding the lines:
18
90 LET T=0
110 delete
120 LET T=T+PEEK(I) and using RUN 90
140 PRINT T
Now delete all the lines from 90 onwards
and SAVE.
Using the Scroll Routine
The following demonstration program
shows in a simple way how the routine
can be used.
With the routine stored in line 10, held
off the screen, enter:
40 for І- 1 TO 23
50 PRINT "LINE ”;I
60 NEXT I
70 POKE 16427,2
80 LET K=USR(16430)
RUN
In line 70 always specify how many lines.
Line 80 calls the scroll routine.
The result of the above program should
be to produce a display in which "LINE
3" is missing, and the remainder of the
display has been scrolled up a line (hence
the gap between "LINE 22" and the error
report).
SYNC Magazine
ERROR А Report
The routine does declare an error when
an attempt is made to hold more lines
unscrolled than actually exist in the display
file at that particular moment. This can
be seen in the demonstration program by
changing line 70 to read:
70 POKE 16427,24
This asks the routine to scroll all the lines
after the 24th. Clearly a confusing situation
An Example Use of Scrolling
The following game shows just one of
the many uses to which the scroll routine
can be put. In this game you will test your
skill at driving along a road. The scroll
routine is used to scroll the “road” and
also to remove an “end message”; in this
case the message is “PRESS 5,6 or 8.”
many lines are to be left unscrolled is
specified on each occasion that the scroll
routine is called.
This game program is really only a first
try at using the scroll routine, so I would
therefore be very interested in seeing
programs from readers who use this routine
so ERROR A is reported. Note carefully how the parameter of how in writing their own programs. a
Road Game
10 as previously prepared and held off the screen.
20 REM STOP » Just а reminder.
30 RAONDOMISE ; Different every run.
40) PRINT , "жжж ROAD GAME sex" ; Title.
эй PRINT ; Space,
ЕЙ LET C=ø ; Cet odometer to zero.
70 GO TO 190 ; бо past subroutine.
ӘЙ LET SzS-RNDCcCS52-3 ; Move road a little left or right,
90 IF 6554 THEM LET S=4 ‚ but not off the left,
100 IF 652250 THEN LET S=20 ; nr off the right.
110 FOR A=1 TO 5-2 ; Print "one mile" of road.
128 PRINT "ИВ": № сн: ++ Ad , Hard verge,
150 NEXT A :
140 PRINT " "5 (4 өр.) ; Print four spaces for the road.
150 FOR A=St2 TO 32 > Тһе other hard verge,
16@ PRINT "В"; В сн: ++ A? i
170 NEXT A ,
180 RETURN ; One mile of road printed.
199 FOR К-і ТО 4 ; Print four miles of road
200 LET $15 >» but fixed; rather than curved.
210 60 SUB 110 ; Each mile.
z2U NEXT R ,
50 FOR R=1 TO 3 ; Now Print three miles of road
240 60 SUB 50 ‚ that does use the random function
2590 NEXT К ; to move the road left or right.
26@ LET Т=119+РЕЕК (1696, › +РЕЕК ‹ ; Initial car position.
16597) ж25Е, 1
270 LET R=T ; Сору it.
220 POKE К, 20 ; Print the car.
230 PRINT , Add an end of line marker.
500 PRINT ; Space.
510 PRINT : "PRESS 5,6 ОК 2" ; Left, right, or straight ahead.
520 INPUT А ; Collect direction.
20 POKE 16427,9 > Hold the title and road unscrol led.
540 LET T=USR( 164309 ; Scroll away the blank lins.
i50 POKE 16427, 9 + Hold the title and road unscrollsd.
360 LET T=USRC 16430) ; Scroll away 'PRESS 5.6 OR 8:
370 IF A=8 THEN LET R=R-CRNDCS) > Turn tO right,» but not always.
ад
290 ТЕ A=5 THEN LET R=R+CRNDCS3 > [urn to left, but not always.
) 2)
i30 POKE 16427,2 +" Hold the title unscrol led.
400 LET T=USR( 164303 ; Scroll the road
410 GO SUB SU ‚ Add another mile of road.
420 IF NOT PEEKCR}I=@ THEN GO ТО > Test to see if runs off road.
450
420 LET C=C+1 > Increment odometer.
440 GO TO 250 з "Survived" so drive on.
450 PONE К, 148 > "CRASHED"
460 PRINT , Add епа of line marker.
470 PRINT ; Space.
бод PRINT "ж YOU CRASHED AFTER , Тһе sign of failure,
July/August 1981
19
Тһе Take-Away Game
Pn
to remove the last coin from the board is the /oser of the game.
Find the Numbers
f we add the digits of a two-digit number together, we get the sum of 5.
Now, if we write this two-digit number down, reverse it, and subtract the
smaller number from the larger number, we find that the difference is 27.
Can you tell us what these two numbers are?
N
АА \
The Farmer and His Four Sons
et’s start off with a game you might care to program for your ZX80
computer. Lay out five rows of five coins each on the table. Each player, in
turn, may remove one or more coins from any row or column of coins.
However, there cannot be a gap between any of the coins. The coins
; removed must be contiguous within the row ог column. To illustrate,
Ж j suppose the first player removes coins number 3 and 4 from the top row of
NÉS coins. His opponent could not then remove coins 1, 2 and 5 from this row
because there would be a gap between coins 2 and 5. This player could,
however, remove coins 1 and 2, or 5 from this row. The person who is forced
х Ден
ООО ОО
O O ОО
O OO O
O O ООО
O O O O OO
ОО
Тмо-Юг-Опе
еге we have two checker puzzles. The first one is а
checker problem and is pictured at the left. White
has the move and should win in seven moves. Can
you solve it? The second problem is straight forward
enough. How many squares are there on a checker-
board? If your answer is 64, sit down and give
someone else a chance. (From Merlin’s Puzzler 3 by
Charles Barry Townsend, published by Hammond,
Inc.)
An Easy Creditor
gentleman was in temporary need of money. A friend
lent him sixty dollars, telling him to repay it in such
sums as might suit his convenience. Shortly after-
wards he made a payment on account. His second
payment was half as much as the first; his third
three-quarters as much, his fourth one-quarter as
much and his fifth two-fifths as much. It was then
found, on striking a balance, that he still owed two
dollars.
What was the amount of the first payment?
(From Puzzles Old & New by Professor Hoffmann
circa 1890)
nce upon a time (now where have I heard that before) a farmer
owned a square field which had four apple trees growing on it. The
trees were neatly spaced in a row as shown in the drawing at the right.
The farmer had four sons that he wanted to divide the field among.
His problem was that each son had to have an identically shaped
piece of the field. Also, each piece had to be the same size in area.
Finally, each piece of the field had to have one apple tree on it. If you
had been the farmer, how would you have divided up the field so that
each of the sons would receive his fair share?
readers of SYNC, send it along. If Merlin uses it, he will send you a copy of
hat’s it for this issue. I hope you have enjoyed the problems brought by
Merlin. If you have a favorite puzzle that you would like to share with the
Merlin’s Puzzler, a great book filled with the best in puzzles and games.
Until next time, keep puzzling!
Your editor, = 2
Charles Barry Townsend Ж 4 © wa
20
Answers on page 27.
SYNC Magazine
S
Fred D’lgnazio and Stan Gilliam have
created a delightful picture book adven-
ture that explains how a computer works
toa child. Katie “falls” into the imaginary
land of Cybernia inside her Daddy's home
computer. Her journey parallels the path
of a simple command through the stages
of processing in a computer, thus
explaining the fundamentals of computer
operation to 4 to 10 year olds. Supple-
mental explanatory information on com-
puters, bytes, hardware and software is
contained in the front and back end
*; new friends
|, ог your child...
Katie and the Computer
Thrill with your chidren as they join the
Flower Bytes on a bobsled race to the
CPU. Share Katie’s excitement as she
encounters the multi-legged and mean
Bug who lassoes her plane and spins her
into a terrifying loop. Laugh at the
madcap race she takes with the Flower
Painters by bus to the CRT.
“Towards a higher goal, the book
teaches the rewards of absorbing the
carefully-written word and anticipating
the next page with enthusiasm...”
The Leader
papers.
“Children might not suspect at first
there’s a method to all this madness—a
lesson about how computers work. It
does its job мей.”
The Charlotte Observer
*...the book is both entertaining and
educational.”
Infosystems
The book has received wide acclaim
and rave reviews. A few comments are:
"Lively cartoon characters guide read-
ers through the inner chamber of the
computer."
School Library Journal
“...ап imaginative and beautifully con-
ceived children's story that introduces
two characters—the Colonel and the
Bug—who already seem to have been
classic children's story book characters
for generations."
The Chapel Hill Newspaper
Written by Fred D'Ignazio and illustrat-
ed in full color by Stan Gilliam. 42 pages,
casebound, $6.95. (12A)
A t-shirt with the Program Bug is
available in a deep purple design on a
beige shirt. Adult size S, M, L, XL.
Children's size S, M, L. $5.00.
To order, send a check for books plus $2.00 shipping and handling per order to Creative Computing, Р.О. Box 789-M, Morristown, NJ 07960. NJ residents add 5%
sales tax. Visa, MasterCard, and American Express orders are welcomed. For faster service, call in your bank card order toll free to 800-631-8112 (in NJ call
201-540-0445). Or use the handy order form bound into this magazine.
INVENTIVE PROGRAMS
FOR THE ZX80 4K ROM/1K RAM
Games, subroutines, and teaching aids in 4 K BASIC
and MACHINE CODE. All listings include statement/
subroutine logic and 8К ROM/16K RAM appendix.
PRICE: $1.00 per program listing
(minimum order 10, plus $2.50 S & H)
PARTIAL LIST * (4K/1K)
* FLIP-A-COIN * TEST PATTERN
* 1 KEY BANDIT * CASSINDEX
* TURRET GUNNER * FOIL FENCING
ж 2X80. BASIC TEST * BANG! FOR 1
* BLACKJACK * EASTER DATE
* FIBONACCI SEQUENCE * STATE CAPITALS TEST
* COORD GRAPHICS
demonstration picture.
ж MACHINE CODE DISPLAY
* BARRAGE * GUILLOTINE
ж ACEY-DUCEY II * KEYBOARD GRAPHICS
* LINE RENUMBER ж 81 BOXES
TO ORDER.
Specify programs wanted and enclose payment.
yet succeeded.
ZETA SOFTWARE
P.O. BOX 3522
GREENVILLE, S.C. 29608
onlyo
* Complete list sent with your order, or send SASE
for FREE list and order blank.
IHGA Иза
ZX80-4K ROM
quality software...
1K Space Intruders $20 ?
Written in machine code
to give fast moving
‘Flicker Free' graphics.
A superb achievement.
Supplied as a listing only.
16K High Resolution $20%
(192x192) graphic pictures
Never before achieved on the ZX80.
Create your own artwork.
as а listing (25.99 extra if cassette
required) with full screen
Supplied
9K Nightmare Park $15 >
A good example of a BASIC
program using MACRONICS
'Amazing Active Display'
The park of DEATH - can
you get through this
nightmare. No human as
Confronted by all sorts of 'Happenings'
you'll be taken to your wits end.
Supplied on cassette
Send International cheque or money order {о :-
MACRONICS, 26 Spiers Close,Knowle, Solihull
West Midlands B93 9ES, United Kingdom
other MACRONICS software available
from IMAGE COMPUTER PRODUCTS
in the United States
Subroutine
10 DIM BC2S)
20 БОК 1=0 TO 23
хо LET BCI) =0
40 NEXT I
So FOR 1=0 TO 23
60 FRINT I
70 INPUT BCL)
Во IF BCI) =0
“О IF ірпо THEN GLO
100 NEXT I
Erase lines 10-100 and
THEN STOr
Setting Up Bar Charts
Jon Passler
A bar chart is one of the most commonly
used methods of graphically presenting
data for quick interpretation. Such charts
work nicely within the constraints of the
ZX80 and MicroAce. Beside making for
a good display, they provide an excellent
way of storing data.
The program listed here works with 1K
to chart two years of monthly checking
account balances with vertical bars. The
graph is set up for a range of $0 to $1500,
but can be modified for other ranges with
use 50
TO 1 instead of RUN hereafter.
Bar Chart Program
100 КЕМ GO TO 1 (Leave cursar on line
110 FRINT 100 when Saving
120 PRINT reminder not to КОМ.)
150 FRINT "X100 AVE DAILY BALANCE" (5 өр.)
140 PRINT "-----(3 sp. and 17 SHIFT G)”
190 РКІМТ
160 FUR, іе TO ©
170 LET Еж (ТУЗ) k1O-TRKLO/S
180 IF K=O AND 15-9 THEN РКІМТ —I3s"-";
170 IF Кер AND I;-10 THEN FRINT " ПЕ (1
200) IF КО THEM PRIN] "=": (2 өр.)
210 FOR J=0 TO 23
S260 ТЕ ВЈ) =0 THEN GO TO 290
2S0 LET DsBHBGDO--IX100
240 IF Dé-225 THEN PRINT " "g (1 sp.)
2300 IF D2—26 AND Dz22 THEM FRINT CHRS (7);
260 IF D524 THEN РКІМТ CHRS$;130)3;
2/0 NEXT J
200 PRINT
270 NEXT I
Ооо PRINT ~” 1980 КӨӘНІРТ E) 191” 4f.
эзо STOP
зо КЕМ Б(16)
22
а few changes and some trial-and-error
experimentation. Of course, any other sort
of data such as monthly rainfall or average
temperatures, miles-per-gallon, electricity
use, or frequency distributions (histograms)
can be plotted.
Because of memory limitations the array
storing the data is created and filled in a
routine that is later erased (lines 10-100).
All elements of the array contain either
data or zeroes, and line 320 is used to
show the user which element of the array
should be filled next. To add a monthly
figure enter 330 LET В(16)= ХХХХ, then
GO TO 330 and N/L, and finally erase
line 330 and update line 320 to REM
B(17).
After entering the program, you can
enter the following data to see how it
works: 1012, 796, 931, 1236, 1252, 1088,
786, 1132, 1194, 908, 1113, 896, 913, 849,
553, 429. "n
Jon Passler, 344 Cabot St., Beverly, MA 01915.
4, and = sp.)
SYNC Magazine
Bisection Iteration
Square Root Program
10 PRINT "SQUARE ROOT OF Xx"
го FRINT "ENTER X "s (3 spaces)
aD INPUT X
40 PFRINT X
52 LET Цео
60 LET H=162
70 LET Тен) 72
GO LET R-X/T
90 IF kef THEN GOTO 160
100 IF H-L < 2 THEN GOTO ТО 160
110 IF Е X T THEN GOTO 140
i20 LET Бет
150 GOTO 79
140 LET HsT
1520 GOTO 79
160 PRINT "ROOT 15 "sl 62 spaces)
170 PRINT
180 STOP
NOW AVAILABLE
| sion
oard
Keyboard vith complete parts and plans $55.00
Wired keyboard, complete with plans $75.00
Mail for information:
L.J.H. Enterprises
P.O. Box 6273, Orange, CA 92667
For information or Visa or MasterCard orders call
(714) 772-1595. Shipping charge for U.S.—$5.00.
July/August 1981
Mike Goins
This program operates by means of
bisection iteration, which is basically just
a variation of the old high-low game. The
size limitation of the integer basic (уап-
able size) limits the maximum root to 181.
Besides the mathematical value, this
Square root program is handy for use as a
subroutine to represent the distance
between two points (using the Pythagor-
ean theorem) in some game programs in
which one might try to guess the location
of an object and when in error to find out
by how great a margin. :
Mike Goins, P.O. Box 3341, Bristol, IN 37620.
SUPER INVASION
ON YOUR ZX80!
SYNC magazine says Super Invasion is the
<.. best action game we have seen for the ZX 80."
DOUBLE BREAKOUT
DOUBLE BREAKOUT challenges you to get through two barricades,
using two ball angles. With seven levels of play, DOUBLE BREAKOUT
is hard to beat. You'll be amazed at the superb
graphics in this 1K game. $14. 95
SUPER ZX80 INVASION
SUPER ZX80 INVASION is a flicker free, moving graphics game with
three levels of play. SUPER INVASION challenges your skill as you
shift your craft left and right and fire lasers at the invading
space ships. Added bonus — each cassette
contains a more sophisticated 2K version. $ 14. 95
23
Multi-Dimensional Arrays for (һе ZX80
Jamie O’Connell
How many times have you sat down to
convert a program for the ZX80, only to
find that the first line was 10 DIM
A(10,10)? Chances are that you gave up
and turned the page. The next time you
do not have to turn the page because it is
possible to simulate dimensioned arrays
on the Sinclair through the use of a simple
algorithm.
Many versions of Basic define a two-
dimensional matrix by the command DIM
A(X,Y); where the X is the row subscript,
and Y, the column. Any location on the
matrix can be accessed by specifying
values for X and Y. For example, LET
A(3,4)=9 assigns the value 9 to the element
located at row 3, column 4.
On the ZX80, we define a one-dimen-
sional/vector array containing as many
elements as we need and then use a simple
formula to locate a given element. For
example, if we want to initiate a 10 by 10
matrix, the instruction DIM A(99) sets up
100 locations and the formula A(X+ Y*10)
—9 assigns to the element at (X,Y) the
value 9. In order to save space, the first
element in the array simulates A(0,0) and
the last, A(9,9). If we take the first element
to be A(1,1) (as it is in most Basics), then
we would use the general formula A((x-
1)+(y-1)*X). These formulae result in
column-order storage: all of column 1 is
stored before 2. To simulate row-order
storage, use the formula A((y-1)+(x-1)*Y)
as in Figure 1.
In similar fashion, arrays of any number
of dimensions can be accessed. The
element A(X,Y,Z.,...) is located at A((x-1)
Z X80 Basic
10 DIM A(59)
20 LET Х-3
30 LET У=1
40 LET 7-2
Tiv-D*X-iz-D*X*Y -G.OTX*Y*Z4-, А
simple comparison shows how the ZX80
can simulate three-dimensional Basic:
3-dimensional Basic
10 DIM A(3.4,5)
20 LET Х-3
30 LET Ү-і
40 LET 7-2
50 LET A((X-1)+(Y¥-1)*3+(Z-1)*3*4)=9 50 LET A(X,Y,Z)—9
ZX80 Simulated Simulated Simulated
Actual Column-order Column-order — Row-order
Location Location Location Location
A(L L=x+y*3
A(0) A(0,0) А(1,1)
А(1) А(1,0) А(2,1)
А(2) А(2,0) A(3,1)
A(3) А(0,1) А(1,2)
А(4) A(1.1) А(2,2)
А(5) А(2,1) А(3,2)
А(6) А(0,2) А(1,3)
А(7) А(1,2) A(2,3)
A(8) A(2,2) A(3,3)
A(9) A(0,3) A(1,4)
A(10) A(1,3) A(2,4)
A(11) A(2,3) A(3,4)
L=(x-1)+(y-1)*3 L-(y-1) + (x-1)*4
A(3,4)
Figure 1. Simulated Locations for a 3 by 4 Array
Jamie O'Connell, Apt. 17 Cricket Brook, Dover,
NH 03820.
24
The best way to illustrate the use of
dimensioned arrays is by a demonstration
program. The one offered below is fun
because the movement of the ship is
essentially random. You can never know
where it is until you blow it up or actually
have it captured. Note that in a 10 by 10
matrix the array location is the same as
the simulated location: A(37) is equivalent
to A(3,7). This allows direct input of the
coordinates desired. The display routine
illustrates a fairly standard procedure for
the printing of a matrix.
Capture
Capture is similar in some respects to
many other matrix manipulation games;
but, instead of trying to hit the enemy,
you must surround and immobilize him.
If you do succeed in hitting his location,
you lose the game.
You have a total of fifteen mines which
you use to block the enemy's progress.
For a capture, his progress must be
blocked in every direction. The display
will show you where he was on the
previous move. You can always place a
mine at this previous location, as he has
to move one space on each turn.
Lines 10-50 set up the enemy’s initial
location. Lines 80-195 output the display
which shows: the matrix, the previous
enemy location, the number of mines left,
and the location of the mines as you place
them. Lines 210-60 decide the enemy's
new location, test for capture, and check
the remaining number of mines. Lines
370-430 input your mine placement coor-
dinates and test for a hit on the enemy.
SYNC Magazine
|
EMT WT
To vary the number of mines, change
line 60. Line 370 was keyed in using the
following space saving technique: 370
INPUT (SHIFT 5) PRINT “ (SHIFT 8)
ROW-COLUMN"'. If you fail to use this,
the program will print error code 4 when
run—every byte counts! When entering
the coordinates at line 370, enter them
both before hitting NEWLINE. Happy
hunting! "s
Capture Program Listing
10 RANDOMIZE
20 DIM A(99)
38 LET X=RND(1@)-1
АЙ LET Ү-ВМр(10)-1
50 LET А(Ү-Х%10)-148
60 FOR M--16 TO 2
76 PRINT
8g PRINT "1 WAS LAST AT,. a"
96 PRINT
100 PRINT " 9123456789"
110 FOR І-й TO 9
120 PRINT Т;
138 FOR J= TO 9
140 PRINT CHRS(A(J+I*19));
150 NEXT J
160 PRINT
176 NEXT I
18% PRINT
190 PRINT "MINES-";-M
195 PRINT
200 LET A(Y4X*10)-g
210 FOR Т=1 TO 64
220 LET I-RND(3)-2
230 LET I=I+X
240 IF I 9 OR I Ø THEN GO ТО 220
256 LET J-RND(3)-2
260 LET J-J4Y
276 IF J 9 OR J Ø THEN GO TO 250
288 IF І-Х AND J-Y THEN GO TO 256
290 IF NOT А(9+1*10)=26 THEN GO TO 339
300 NEXT T
310 PRINT "OOPS-CAPTURED"
320 STOP
338 LET X-I
ЗАЙ LET Y-J
350 LET A(Y«4X*19)-148
366 IF M=@ THEN GO TO 440
376 PRINT " INPUT ROW-COLUMN"
380 INPUT R
398 IF A(R)-148 THEN GO TO 460
416 CLS
420 LET A(R)=2¢
438 NEXT M
448 PRINT "OUT OF MINES"
450 STOP
468 PRINT "YOU BLEW ME UP"
July/August 1981
Capture Sample Run
I WAS LAST AT...
0123456789
МО oN ОМА > бо го н О
MINES=16
INPUT ROW-COLUMN
17
I WAS LAST AT...
0123456789
O
T ж
2 ж *
3 х х ж ж
4 B -*
5 хх ж *
6
Т
8
9
MINES=3
INPUT ROW-COLUMN
45
I WAS LAST АТ...
01234567
0
1 ж
A ж ж
3 хх * X
4 х Щщ х
5 ххх
6
f
9
9
MINES=2
OOPS-CAPTURED
8 9
25
TRS and LET AS=AS-+BS оп the 7Х80
Harry Doakes
String handling on the ZX80 is reason-
ably good. The 4K Integer Basic lets the
user print, input, and compare strings,
and do specialized routines that will
transform numbers into strings or charac-
ters.
There are also some large holes in its
string handling abilities though such as
limited string truncation and no conca-
tenation. It is not hard to figure out why:
Integer Basic takes up less than 3600 bytes
of space, since the character generator,
about 500 bytes long, is also in the 4K
ROM. The only command for changing
the size of a string is TL$ (which stands
for Truncate (shorten) from the Left of
the String). PRINT TLS(“FRED”) produces
“RED”; TLS chops off the leftmost char-
acter of the string in parentheses whether
it is a literal string (like “FRED”) or a
variable (A$, for example). With TL$ you
can trim as much as you like from a
string—but only one byte at a time, and
only from the left side.
Sinclair’s Integer Basic has no string
concatenation commands at all. In other
words, there is nothing like LET A$=A$+
В$. You cannot lengthen a string.
Other small Basics—for example, Radio
Shack’s Level 1—allow fewer string vari-
ables and only INPUT and PRINT com-
mands. The ZX80 looks good by compar-
ison, but comparison cannot fill those string-
handling holes.
This program can.
Enter the program in Figure 1. Line 10
should contain 52 zeroes.
10 REM 00000000000000000000000
00000000000000000000000000000
20 FOR А=1 TO 52
30 PRINT A;" ";
40 INPUT B
50 POKE 16426+А,В
60 PRINT В,
70 МЕХТ А
80 INPUT A
90 IF A=O THEN STOP
100 INPUT B
110 POKE 16426+A,B
120 PRINT As" ";В,
130 GO TO 80
Figure 1.
Harry Doakes, P.O. Box 10860, Chicago, IL
60610.
26
Run the program and enter the following
numbers in order. The numbers in paren-
theses are just entry numbers. Do not key
them in.
(1) 175 (2) 235 (3) 30 (4 10
(5) 197 (6) 225 (7) 57 (8) 235
(9) 249 (10) 235 (11) 227 (12) 43
(13) 43 (14) 43 (15) 40 (16) 9
(17) 227 (18) 209 (19) 213 (20) 227
(21) 35 (22) 3 (23) 3 (24) 24
(25) 21 (26) 60 (27) 237 (28) 185
(29) 35 (30) 235 (31) 33 (32) 0
(33) О (34) 35 (35 12 (36) 32
(37) 252 (38) 4 (39) 32 (40) 249
(41) 227 (42) 193 (43) 213 (44) 227
(45) 35 (46) 35 (47) 237 (48) 176
(49) 235 (50) 227 (51) 249 (52) 201
When you have keyed in the 52nd value,
stop and proofread the contents of your
screen very carefully.
If you find a mistake, type the entry
number, hit NEWLINE, then enter the
correct value. The new version will appear
at the end of the list of numbers. When
you have corrected all mistakes, enter 0.
The program listing should now look
something like Figure 2. Delete lines 20
through 130, and you are ready to key in
your Own program.
You now have two new string functions.
The first will truncate a string from the
right side; a TRS, if it existed, would do
the same thing. To perform the equivalent
of
LET G$=TRS(G$)
you write:
LET G$=G$
RANDOMISE USR(16428)
After the routine is complete, a PRINT
G$ would show that the final character is
gone.
The second function is even more useful;
it is the equivalent of
LET L$=L$+M$
The appropriate program lines are:
LET L$=L$
LET M$=M$
RANDOMISE USR(16427)
At the end of the routine, M$ no longer
exists, and L$ contains both strings.
Each function will work with any string
variable, A$-Z$.
A few caveats:
You must perform the LET commands
immediately before the USR line. LET
creates a new entry at the end of the list
of variables in RAM. By performing those
LETS, you put the strings you are working
on at the end of the variable list so the
USR routine knows just where to go to
find them.
You can substitute LET, PRINT,
IF...THEN, and most other commands
for RANDOMISE. Remember, though, if
10 REM FOR 2m? OR Т FOR CONT
ПИЈЕ FOR =FFFC#E? THEN =7mm</W Р
ОКЕ M7 FOR 5 7£4 LOAD "4 CONTIN
UE =? THEN =77 POKE ЖЕОК = CONTI
NUE ?
Figure 2.
you create a new variable with LET, you
will have to LET AS—AS etc. again before
performing any more of these string func-
tions.
Do not try to ТК$ a string with nothing
inside. You can do it if, for example,
05=“ "—рш not if Q$—*". И CODE
(Q$)=1, do not use the TRS routine.
These routines will not work with
literals— only string variables. You must
put a string into a variable before you can
perform these operations on it.
SYNC Magazine
1
E
If you want to use line 10 for your
program, you can renumber the REM
line using the EDIT function. It will work
without change if it is still the first line of
the program; if not, you will have to find
its new location to call the routines with
USR. The routines should never begin
beyond 16639, or you will have to alter
the machine language program.
Figure 3 lists the routine in assembly
language. The procedure is relatively
straightforward. Each routine loads HL
with the E-LINE value (which points to
the end of the variable list); finds the end
of the variable it wants to work on; shifts
the variable list down, one byte at a time,
until it reaches the end of the list; then
loads the new value of E-LINE into the
proper location.
Parts of the routine may seem more
complicated than necessary. The extra
code is used to avoid instructions using
values between 64 and 127 decimal (40h-
7Fh). These values cause screen distortion
and quickly crash the system if the ZX80
tries to display them as characters in a
string or program line. A program that
cannot be safely listed is too impractical
for general use, so this one avoids those
values. The routine begins, for example,
not with LD HL, (400A), but with a longer
instruction sequence that avoids the unlist-
able values.
At the beginning of the routine, certain
things are taken for granted: BC=0, the
Z flag is reset, and H=40h. The first two
are always true when a routine is called
with a USR command. The third is true
for any routine between USR(16384) and
USR(16639), since the ZX80 simply loads
HL with the starting point and does a JP
(HL).
Finally, notice that the end of the routine
HL=SP. Thus, PRINT USR(16427) will
not only add two strings together, but will
also tell you where the top of available
memory is. PRINT USR(16427)-PEEK
(16400)-256*PEEK(16401) will return the
amount free memory remaining—but be
sure that you have the strings in place to
be worked on, or you will scramble your
variables and you may crash the sys-
tem. 2"
decimal hex assembler
112 AF XOR А
ЖЫ ЕВ ЕХ DE, HL
20, 19 1ЕОА LD Е, OAh
197 C5 PUSH BC
225 E1 POP HL
57 59 ADD HL, SP
cog EB EX DE, HL
249 F9 LD SP, НІ,
255 ЕВ ЕХ DE, HL
227 E3 EX (SP), HL
43 2B DEC HL
43 2B DEC HL
43 2B DEC HL
40, 9 2809 JR 2, O9h
227 ЕЗ EX (SP), HL
209 D1 POP DE
215 D5 PUSH DE
22T E3 EX (SP), HL
55 22 INC HL
2 05 INC BC
5 05 INC BC
24, 21 1815 JR 15h
60 56 INC А
237, 185 EDB9 CPDR
25 25 INC HL
299 ЕВ EX DE, HL
25, 0,0 210000 LD HL, 0000
25 25 INC HL
12 OC INC C
ја. 258 20FC JR №, FCh
4 04 INC В
22, 249 20F9 JR NZ, F9h
бел Ез ЕХ (SP), HL
193 C1 POP BC
215 D5 PUSH DE
227 Е5 ЕХ (SP), HL
25 22 INC HL
25 25 INC HL
237, 176 EDBO LDIR
255 EB EX DE, HL
227 ЕЗ ЕХ (5Р), НІ
249 FQ LD SP, НГ
201 C9 RET
Figure 3.
А=О, 221
D=40h
EzOAh
НІ-О
HL=SP
DE-SP, НІ-400АҺ
SP=400Ah
HL=SP
HL=(400Ah), (SP)=SP
(HL)=80h
D -O01h
(HL)=character
jump to $+$
DE= HL
(DE)=character
(HL)=Oth
BC=0002h
jump to finish
$+$: A=Oth
BC=displacement
22.
(DE)z01h
HL=0
НТ=-ВС
BC=HL=displacement
HL=DE
(HL)=character
finish: shift until
BC=0, DEZE-LINE
HL=SP, E-LINE=E-LINE
sP=SP
Duzzie answers
Find the Numbers: 41 and 14
Two-for-One: (A) White to move and win: 26-
22, 18-25, 21-17, 14-21, 19-16, 12-26, 27-31. (B)
There are 204 squares in a checkerboard. Some
are single squares, some are made up of 4
squares, 9 squares, and so on.
July/August 1981
The Farmer and His Four Sons:
An Easy Creditor: The amount of the first
payment was $20. To ascertain this amount, let
x = the first payment. Then according to the
conditions of the puzzle:
X 3x X 2x
xt + 4 + 4 777% + 2 = 60
Multiplying by 20, the least common multiple
of the various denominators,
20x + 10x + 15x + 5x + 8x +40 = 1200
58x = 1200 - 40 = 1160
x = 20
27
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Тһе ZX80 Makes the Grade
Lawrence Auer
Introduction
It is not a toy! Even with only 1K bytes
of storage, the ZX80 can be an invaluable
aid to the teacher in the calculation and
evaluation of grades. In this article we
present two programs running on the 1K
Basic machine. The first determines the
test scores and keeps track of which
question caused the class the greatest
difficulty. The second finds the class
distribution of grades, enabling the teacher
to scale the grades. While with more
memory the two programs can be easily
combined, presentation of the separate
codes is made for those, like me, who
want to do something while they wait for
the 16K memory to arrive.
These programs have been used to
handle the bi-weekly exams of twenty
questions given to the 95 students in my
introductory astronomy class. While, in
principle, the same sort of computations
could be accomplished at the university
main frame computer, there is no compar-
ison between that and a comfortable chair
in front of the TV апа 7Х80. Further,
because of the way the programs are set
up, the data can be entered piecemeal,
with more being added at your con-
venience. Finally, the tape storage system
makes it a trivial task to keep the results
for all the tests together. You can mount
the cartridge and “instantly” see how the
class did on any exam.
Program 1: Test Scoring
Using the ZX80 to add the scores on
questions is an obvious and useful applica-
tion. The ZX80 can be even more useful,
however, because it can also keep track
of which questions are being missed. After
all the tests are graded, the teacher has a
measure of which concepts were the
hardest for the students. Knowing the
Lawrence Auer. 1301 Park Hills Ave.. State College.
PA 16801.
July/August 1981
question-by-question scoring, the teacher
can see exactly which topics need review.
Before using the first program, edit lines
10 and 11. N is the number of questions
on the test (20 or fewer; more may cause
memory overflow). P is the default number
of points per question. This number is
used for the default when no number is
explicitly entered in answer to the prompt
at line 136. The reason for having a default
P is that most answers are right (we hope!)
and it is needless to have to enter numbers
when just a single NEWLINE will do.
Having defined N and P appropriately,
we can now enter the data. In response to
the prompt “О”, where О is the number
of the question whose score is being
requested, reply with the value earned.
As described above, NEWLINE by itself
will give the default value, P. Any other
number is simply typed in the normal
manner. The characters “К” and “Е” are
special and are interpreted as follows: 1)
“К” stops (1.е., "kills") the program at this
point. You can resume grading at exactly
this point at a later time simply by using a
CONTINUE command. More on this
below. 2) “Е” means the last score entered
was in "error." The score is erased, and
you are asked to correct its value.
After the scores on each question have
been entered, the student's total is given.
At this time you can get a plot of the
relative number of points lost per question
by typing "P" in answer to the prompt.
The length of the bar is proportional to
how many fewer points were earned by
correct answers to this question than the
one that earned the most points. Note
that the shortest bar is the question the
students did best on. The numeric value
of the plotted quantity is listed at the end
of the bar. After looking at the plot, you
can either kill the program with "K" or go
back to enter another exam by typing
NEWLINE.
After stopping the program by entering
“К” at any time, it may be SAVEd. АП
the relevant information is stored. The
program and data may be LOADed, and
you will start at the place where you
stopped simply by executing
CONTINUE.
Program 2: Grade Distribution
The overall performance of the class is
determined by entering the test grades
into Program 2. Grades are assumed to
be in the range 0 to 100. A different range
is easily accommodated by modification
of the scaling used in line 225. Instead of
5, use another number which maps your
input into the range (0,20). After a grade
is entered, a plot of the number of students
receiving a grade in each indicated interval
is made. The first number in a row is the
grade interval being plotted. The length
of the bar labeled with the value G in the
first column is proportional to the number
of people who scored in the range, G to
G +4; e.g., the bar labeled 75 contains all
who scored 75 to 79. The second column
contains the number who scored in this
range; the bar length is proportional to
this figure. The third is the cumulative
distribution, i.e., how many were in this
grade range or lower. The cumulative
distribution is particularly important
because it indicates the relative merit of a
given absolute grade. The last value in
this column is always just the number of
test grades entered so far.
As in Program 1, the letter "E" entered
instead of a grade deletes the grade just
entered, i.e., it erases the error. If you
type the letter "K", the program will stop.
CONTINUE will start you again. SAVE
preserves all data as well as the program,
so you do not have to enter the grades
again if something prevents you from
finishing in one session.
Programming Suggestions of General
Applicability
Several programming techniques used
in these codes will be useful in other
Z X80 programs.
When you have to enter the grades for
95*20— 1900 answers, most of which are
for full credit, you can get very tired of
typing “5” then NEWLINE. It is much
more efficient simply to type NEWLINE
(NL in prompts) and let the machine make
the default. Unfortunately, if you are
INPUTing into a numeric field, NEWLINE
by itself is ignored; thus, you have to use
a string variable for INPUT. In this case,
NEWLINE by itself sets the string to be
the null string, “”. The price paid is the
31
need to convert any non-null string to а
numeric value. For example, one has to
set G=15 when the input is the string
“15”, i.e., characters “1” and “5”. The
requisite code is in lines 148-151 of Program
1. Line 152 takes care of the default for
null strings. Note the use of the operator
“ ”, which permits the code to work
even if A$ is initially null.
It is human (rather than machine!) to
want to use mnemonic notation to enter
signals for action. That is, when you want
something erased, it is more natural to
type “E” than to enter the value 101.
When the input is being made into strings,
it is no problem to check whether the
string is the symbolic signal. This is the
technique used in Program 1, line 265. In
Program 2 the input is numeric, however.
In order to use the letters “K” and “E” as
symbolic signals there, we have to be a
little more tricky. What we do in lines 3
and 4 of Program 2 is to define the variables
Е and К, giving them appropriate numerical
values. The text typed in response to an
INPUT statement is evaluated before being
stored into the destination. Thus, typing
E in response to the INPUT statement in
line 200 is equivalent to entering the
number 101. Typing the letter K there
sets G=K=-1 and this value of С triggers
the STOP command in line 201. As each
of these variables can be set to any
appropriate "impossible" test scores, it is
no problem to make modifications if
grades 100 are allowed. Finally, if you
prefer, more dramatic and memorable
variable names like KILL or ERASE can
be used.
The CONTINUE Command
Of all the pieces of hidden gold in the
ZX80, the most valuable is the command
CONTINUE. When you leave the program
execution mode either voluntarily because
of a STOP statement in your program or
involuntarily because of an error (like
trying to write too much on the screen),
the place you were when you stopped is
remembered. While in immediate mode,
you can do what you want, including
resetting variables and even editing the
program. The CONTINUE statement will
start you again at the line following the
one where you stopped. Thus, in these
programs you can kill (i.e., “К”) whenever
you want, then SAVE the file on tape.
The LOAD operation brings in the file
with the program, all the data, and even
the information on where you stopped.
CONTINE following the LOAD acts just
as if there had been no tape storage in
between. That is, SAVE followed by LOAD
completely re-establishes the environment
as it was before the SAVE operation. The
only thing to remember if you are going
to use the STOP-CONTINUE trick is to
make sure that the statement following
the STOP produces a recognizable cue.
If you just have the sequence, 100 STOP,
110 INPUT X, when you restart with
CONTINUE you will have a nice blank
Program 1: Test Scoring
screen and the cursor waiting for input
with no hint as to what input is wanted.
To avoid this problem in Program 1, for
example, line 139 jumps back to the input
prompt, so you can tell what is expected
when you restart.
One of the problems in having only 1K
of memory is that peculiar errors can
occur when you are OUTPUTing. The
characters to be written on the screen
occupy the same memory as your program.
You can, therefore, be running quite nicely,
entering question scores, and then have
trouble when you try the plot, because
you do not have enough memory for the
output. The choices made for the scaling
of the bar lengths in these programs work
well for my exams with 20 questions and
95 students, but there may be something
unusual about your distributions. If you
do have trouble, do not panic! Simply
change the scaling; reduce the 15 in line
226 of Program 1 and/or the 20 in line
120 of Program 2. None of the data will
be lost as long as you use CONTINUE to
restart.
More memory will permit these programs
to be significantly improved. Programs 1
and 2 could then be combined so that all
you would ever enter would be the question
scores. Also, one could add a subroutine
which would give the test grade above
which a specified fraction of the class
scored. Finally, with 16K you should be
able to store the names with the grades
and thus have your “mark book" on tape.
In any case, I hope that you find these
programs as useful as I have even in their
limited form.
10 LET N - 20 144 LET 5(1) = S(I) - G
11 LET P = 5 145 СОТО 135
20 DIM $ (м) 148 LET G = 0
25 LET T 3 0 149 LET G = 10*G + СОРЕ(А5) - 28
100 CLS 150 LET A$ = TL$(A$)
105 PRINT "SCORES?" 151 IF А$ > "" THEN GOTO 149
110 LET T = T + 1 152 IF G < 0 THEN LET С = P
115 LET В = 9999 153 PRINT С
116 LET 0 = 0 155 LET Z = Z + С
120 LET Z = 0 160 LET S(I) = 5(1) + G
130 FOR I = 1 TO м 165 IF S(I) < R THEN LET В = 5(1)
135 PRINT "0";7; 166 IF S(I) > 0 THEN LET Q = S(I)
136 INPUT А? 170 NEXT I
137 IF NOT A$-"K" THEN GOTO 140 171 LET R = Q- В
138 STOP 175 PRINT "P TO PLOT',
139 GOTO 135 200 PRINT "GRADE",Z
140 IF NOT AS="E" THEN GOTO 148 205 INPUT A$
141 CLS 210 ІР NOT A$ = "р" THEN GOTO 100
142 LET I = I - 1 215 CLS
143 LET 2 = 2-6 216 PRINT "REL ERRORS"
32
SYNC Magazine
220
216
220
221
225
230
235
240
245
FOR I = 1 TON
ТР I < 10 THEN PRINT " ".
PRINT Is" ";
LET Z = 15*(Q - S(I))/R
IF Z = 0 THEN GOTO 233
FOR J = 1 TO 2
PRINT CHR$(128);
NEXT J
PRINT "Ш";0-5(І)
NEXT I
PRINT "K TO KILL"
INPUT A$
IF A$ - "K" THEN STOP
GOTO 100
Program 2: Grade Distribution
REM GRADE HISTOGRAM
LET K = -1
LET E - 101
DIM C(20)
LET A = 0
LET N = 0
LFT $ = 1
LET G = 0
FOR I = 0 TO 20
LET G = G + C(I)
LET L = 20*C(I)/S
IP I < 2 THEN PRINT " 8:
PRINT 5*I
IF C(I) < 10 AND I < 20 THEN PRINT
PRINT C(I);"B";6;
IF L = 0 THEN GOTO 150
FOR J = 1 TOL
PRINT CHRS(128)
NEXT J
PRINT "Д"
NEXT I
IF N > 0 THEN PRINT "AV-";A/N;
REM K=KILL(STOP), E=ERRCR
PRINT " GIVE GRADE, К OR E"
INPUT G
IF а > К THEN GOTO 205
STOP
SOTO 100
IF С < 5 THEN GOTO 215
LET D = -1
LET G =
GOTO 220
LET D =
LET 0
LET N
LET A =
G
8
C
Q
* D
+ D*G
5
C(G) * D
5 THEN LET 5 =
|
Ql р» 23 a =
yun
LET
LET
IF
CLS
GOTO 100
July/August 1981
с (6)
Blank Cassettes
The quality of cassette tape used to
save and load programs is an important
factor in getting the programs to run.
Tape quality for computers is measured
differently from quality for audio tape.
The tape must be capable of sending to
the computer the electronic signals of
the program without transmitting extra-
neous noises that could interfere with the
ability of the computer to load the tape.
Our blank cassettes are tested and
recommended for computer use. C-10
cassette, 5 min. per side, blank label on
each side in a Norelco hard plastic box.
[0010] $1.25 each.
Head Cleaner
After hours of use, the read/write head in
a cassette recorder will pick up minute
particles of tape oxide. This dirt will hardly
be noticable in dictation or music. But it is
very noticable in computer use. One dropped
bit in 16,000, and the program won't toad.
Help keep your recorder in top shape
with our non-abrasive head cleaner. It consists
of 18 inches of stiff cleansing fabric-in a
standard cassette sheii. One 10-second pass
every 40 hours of use will keep your heads
as good as new. [0011] $2.00. Send pay-
ment plus $1.00 Shipping per order to:
Peripherals Plus
39 East Hanover Avenue
Morris Plains, М.) 07950
MUSIC! for 4K ROM, 1K or more RAM. 2
octaves, 127 note length, any tempo.
Songs repeat. Random sounds also. Cas-
sette and insts. $6.95 pp. $10. outside
U.S. Wm Don Maples, 688 Moore St.,
Lakewood, CO 80215.
>» < тұтты» тұқ» тұты» тұта» TØ
ое 996 C. 4 oC.
Find 7Х-80
Owners
Advertise in SYNC, the magazine ex-
clusively dedicated to the Sinclair ZX-80
and The MicroAce. Call or write for de-
tails and a rate card. Let SYNC readers
know who you are.
SYNC
39 E. Hanover Ave.
Morris Plains, New Jersey 07950
33
Multiplication
Three-in-a-Row
Austin R. Brown, Jr.
“Multiplication Three-in-a Row” is based
on the program “Multiplication Bingo,”
by Jean Wilson, Special Education teacher
at Leadville High School, Leadville,
Colorado. She was seeking a way to
motivate students who were having diffi-
culty learning to multiply and found that
completing five in a row on a Bingo board
helped supply the motivation. An array 5
by 5 is too big for the ІК ZX80, but 3 by 3
will fit.
The game proceeds as follows. You
select a square on the board. You are
then given a multiplication problem to
solve. If you solve it within two tries, an
“Х” goes in the square. If you fail, an “О”
goes in the square. If you get three X’s in
a row before the board is filled, you win.
See Sample Run 1.
The program can be used to build skills
in mental arithmetic, pencil and paper
arithmetic, or calculator arithmetic. It can
generate other ranges of problems by
changing lines 120-130. For example, use
RND(19) rather than RND(9) to generate
factors into the teens.
This is not a tic-tac-toe game. The
number or location of 0’s does not matter,
as long as you can get three in a row by
the time the board is filled.
Programming Notes
The program is built upon the array
U(N), N=1,...9, where М represents опе
of the squares on the board. If the square
has not yet been used (the number of the
square still shows in the display), U(N)=0.
If the player has successfully solved a
problem at that square, “X” shows in the
display, and U(N)=1. If the player has
failed to solve a problem at that square,
“0” shows in the display, and U(N)=2.
Austin R. Brown, Jr., 407 Peery Parkway, Golden,
CO 80401.
34
Use of the array helps the program
logic in several ways, as shown in Listing
1. First, we can generate and update the
display without the need for nine different
string variables and the repetitious logic
they require (lines 740-890). Second, we
can easily check for an already occupied
square,, since U(N) will no longer be zero
(line 110). Third, we can also check for
three-in-a-row, since we have success if,
and only if, all three U's, and hence their
product, are equal to one (lines 230-380).
Fourth, we can easily tell when the game
is over. As long as there is at least one
unoccupied square, its U is zero (lines
300-320). Fifth, we record a right or wrong
answer simply by changing the current U
(lines 190 and 510).
Tic-Tac-Toe
The program can easily be adapted to
a tic-tac-toe game either for two players
or for one player against the computer.
Success for “О” is tested as well as success
for ^X" in lines 230-280, except that the
product must be eight.
Listing 2 shows the program modified
for a two-person game, with the computer
simply keeping track of the action. Sample
Run 2 shows a game. Modifying the
program to play computer against human
is left as an exercise for the reader. For
example, a simple strategy of random
moves by the computer could be imple-
mented by the following changes:
74 IF J=2 THEN GO TO 500
500 LET N=RND(9)
510 IF NOT U(N)=0 THEN GO TO 500
520 GO TO 120
This strategy can be bewildering to the
human encountering it for the first time.
Notes:
REMarks should not be entered into
the ZX80. They are included strictly to
show the program logic. "n
Three-in-a-Row
5 REM Multiplication 3-in-a-row
6 REM A.R.Brown,Jr. 6/1/81
T REM Initialize
10 RANDOMIZE
20 DIM U(9)
30 FOR Т=1 TO 9
ЦО LET U(I)z0
50 NEXT I
60 GO SUB 700
75 REM Pick square
80 PRINT "WHICH SQUARE?"
90 INPUT N
100 GO SUB 700
110 IF М<1 OR М>9 OR NOT U(N)=0
THEN GO TO 80
115 REM Generate problem
120 LET A=RND(9)
130 LET В-ЕМр(9)
140 PRINT "SQUARE ";N
160 PRINT "WHAT IS ";A;"*";p;"?
170 INPUT C
175 REM Check for correct answer
180 IF NOT C=A*B THEN GO TO 500
185 REM Right answer
190 LET U(N)=1
200 GO SUB 700
210 PRINT "RIGHT"
220 PRINT
225 REM Check for 3 іп а row
230 FOR K=1 TO 3
240 IF U(K)*U(K+3) *U(K+6)=1 THE
N GO TO 900
250 IF U(3*K-2) *U(3*K- 1) *U(3*K)
=1 THEN GO TO 900
260 NEXT K
270 IF U(1)*U(5)*U(9)s1 THEN GO
TO 900
280 IF U(3)*U(5)*U(7)s1! THEN GO
TO 900
295 REM Check for end of game
300 FOR Is! TO 9
310 IF 0(І)-0 THEN GO TO 80
320 NEXT I
355 REM Losing end
360 PRINT "SORRY, YOU LOSE"
370 GO TO 999
495 REM Check error
500 IF F»0 THEN GO TO 600
505 REM 2nd time, answer & move
510 LET U(N)s2
520 GO SUB 700
530 PRINT A;"*";pB;"z";A'*B
540 GO TO 300
595 REM 15% time, try again
600 LET Е=-1
610 PRINT "WRONG,"
620 GO TO 160
695 REM Output tableau
Ров CLS
110 LET Fs]
720 PRINT "MULTIPLY 3-IN-A-ROW"
730 PRINT
740 PRINT "и;
T50 FOR 121 TO 9
760 LET A$zSTR$(I)
770 IF Џ(1)=1 THEN LET А%-"Х"
780 IF Џ(1)=2 THEN LET A$="0"
T90 PRINT A$;
800 IF NOT 1=3%(1/3) THEN PRINT
"М"; (Shift Я; 1 time)
810 IF І-3 OR І-6 THEN GO SUB 8
820 NEXT I
830 PRINT
840 PRINT
850 RETURN
860 PRINT
870 PRINT ННН"
(Shift А; 11 times)
880 PRINT " u-
890 RETURN
895 REM Winning end
900 PRINT "-- HOORAY, YOU WIN -
Listing 1.
SYNC Magazine
Sample Run 1
MULTIPLY 3-IN-A-ROW
WHICH SQUARE?
SQUARE 1
WHAT IS 9*8?
We gave T2 for the answer
MULTIPLY 3-IN-A-ROW
WHICH SQUARE?
SQUARE 5
WHAT IS 6*9?
WRONG,
WHAT IS 6*9?
We gave first 69, then 5H
for the answer
MULTIPLY 3-IN-A-ROW
WHICH SQUARE?
SQUARE 9
WHAT IS 7*1?
WRONG,
WHAT IS 7*4?
We gave first 21, then 14
for the answer
MULTIPLY 3-IN-A-ROW
July/August 1981
Tic-Tac-Toe
Я о л
10
20
30
40
50
60
65
69
70
72
74
80
90
100
110
REM Tic-Tac-Toe
REM A.R.Brown,Jr. 6/6/81
REM Initialize
RANDOMIZE
DIM U(9)
FOR I=1 TO 9
LET U(I)=0
NEXT I
GO SUB 700
LET 4-0
REM Pick square
LET Ј=Ј-(Ј/2)%241
ТЕ 4-1 THEN PRINT "X MOVES
IF 4-2 THEN PRINT "0 MOVES
PRINT "WHICH SQUARE?"
INPUT N
GO SUB 700
IF М<1 OR М>9 OR NOT U(N)=0
THEN GO TO 80
120
130
225
230
239
240
0
245
*К)
250
0
260
265
270
0
215
280
0
295
300
310
320
360
370
695
700
710
720
730
740
750
760
770
780
790
800
п ||
810
60
820
830
840
850
860
870
880
890
895
900
910
LET U(N)=J
GO SUB 700
REM Check for 3 in a row
FOR К=1 TO 3
LET I=U(K) *U(K+3) #U(K+6)
IF I=1 OR I=8 THEN GO TO 90
LET І-0/(3%К-2)%0(3%К-1)%0(3
IF I=1 OR I=8 THEN GO TO 90
NEXT K
LET 1=0(1)%0(5)*0(9)
IF I=1 OR I=8 THEN GO TO 90
LET I=U(3) #U(5) *U(7)
IF I=1 OR I=8 THEN GO TO 90
REM Check for end of game
FOR I=1 TO 9
IF U(I)=0 THEN GO TO 70
NEXT I
PRINT" - TI E -"
GO TO 999
REM Output Tableau
CLS
LET Е-1
PRINT "TIC-TAC-TOE"
PRINT
PRINT T п;
FOR I=1 TO 9
LET A$=STR$(I)
IF U(I)=1 THEN LET A$-"x"
IF U(I)z2 THEN LET A$="0"
PRINT A$;
IF NOT І-3%(І/3) THEN PRINT
ms (Shift А; 1 time»
,
IF I=3 OR І-6 THEN GO SUB 8
NEXT I
PRINT
PRINT
RETURN
PRINT
СОВЫ ШЕБЕР
PRINT " 5:
RETURN
REM Winning Ends
IF І-1 THEN PRINT "X WINS "
IF І-8 THEN PRINT "0 WINS "
Listing 2.
Sample Run 2
ТТС-ТАС-ТОЕ
Х МОУЕ5,
WHICH SQUARE?
X chooses 5.
TIC-TAC-TOE
О MOVES,
WHICH SQUARE?
O chooses 8.
TIC-TAC-TOE
X MOVES,
WHICH SQUARE?
X chooses 7.
TIC-TAC-TOE
О MOVES,
WHICH SQUARE?
O chooses 3.
35
А murder has been committed and the
perpetrator has threatened to strike again!
It is up to you to uncover the two pieces
of evidence which will identify the murderer
before he can carry out his threat.
The game consists of searching the 4
rooms in the building where the crime
occurred for the incriminating weapon
and fingerprints. Your initial location is
randomly selected as are the locations of
the gun and the prints. The amount of
time allocated to you ranges from 6 to 30
minutes. To remain in your current position
or to move in either a clockwise or counter
clockwise direction requires from 1 to 5
minutes. A diagonal move can take from
2 to 9 minutes.
To search for one piece of evidence
requires from 1 to 5 minutes; to search
for both requires from 2 to 9 minutes. If
your allotted time drops below 6 minutes
one of your associates may search a room
for you and declare it “clean” and therefore
you do not have to search it yourself,
although you already may have done so.
If you run out of time, the locations of
the fingerprints and the gun are displayed.
If you locate the evidence, the amount of
time remaining is printed.
The program is loaded in three sections.
First, an array of 72 print characters is set
up. This array contains the floor plan
display.
DIM А(71)
FOR I = 0 TO 71
1000
1010
1020
1030
1040
1050
1060
1070
PRINT І + 1,
INPUT K
LET A(I) = K
PRINT ACT)
NEXT I
Drew Nisbet. 6 Moffatt Crt.. Toronto, Ont.. Canada.
М9УДЕІ.
36
Run this portion of the program апа
input the 72 character codes listed below.
If you make an error in entering the values,
Ж Drew Nisbet
you can either rerun the routine or correct
individual entries with a LET statement
(e.g., LET A(O) = 135).
135,131,131,131,181,131,131,1381,131,131,131,134
IF (1/12) * 12 = I THEN CLS
0, 0, O, 31, 0,130
0,133, 3, 0, 3,132
0, 0, 0, 0, 0,130
0, 0, 0, 32, 0,180
0,133, 3, 8, 3,132
After the first portion has been run,
delete lines 1010 to 1070 inclusive and
enter the following lines:
170 LET K = 0
180 FOR I = 1 TO 6
190 FOR J = 1 TO 12
200 PRINT (CHRS(AC(K));
210 LET K = K + 1
220 NEXT J
230 PRINT
240 NEXT I
250 STOP
SYNC Magazine
Key СО ТО 170 and NEWLINE and
check the display. If it requires correction
use a LET statement as above. If the
display is functioning properly, it would
be a good idea to save the partial program
at this point.
Now enter the main body of the
program:
100 RANDOMISE
110 LET G = RND(4)
120 LET P = RND(4)
130 LET R = RND(4)
140 LET M = RND(25) + 5
150 LET GF = 0
160 LET PF = 0
Delete line 1000 and save the program.
To execute, key GO TO 100 rather than
RUN as the latter will clear the print
codes stored in array “A”. This program
could easily be altered in order to create
other “Search and Find” games. By chang-
ing the names of the articles to be searched
LOCATION OF GUN
LOCATION OF PRINTS
STARTING ROOM
AMOUNT OF TIME
GUN FOUND SWITCH
PRINTS FOUND SWITCH
250 PRINT "ROOM-";R,"TIME-";M
260 ТЕТ Q = RND(5)
270 PRINT “SEARCH?”
280 INPUT 1$
TIME FOR CIRCULAR MOVE
290 IF 1$ = “№ THEN GO TO 470
800 PRINT “1-GUN”
802 PRINT “2-PRINTS”
804 PRINT “3-BOTH”
310 INPUT Е
320 LETM =M- 9
330 IF F = 3 THEN LET M=M- G
340 IF M < O THEN GO TO 600
850 IF Е = 2 THEN GO TO 430
380 IF NOT G = R THEN GO TO 420
390 LET GF = -1
400 PRINT “GUN FOUND”
420 IF F = 1 THEN GO TO 460
430 IF NOT P = R THEN GO TO 460
440 LET РЕ = -1
450 PRINT “PRINTS FOUND”
CHECK FOR GUN
CHECK FOR PRINTS
460 IF GF AND PF THEN GO TO 700
470 LET T = RND(4)
480 IF M < 6 AND NOT (T = G OR T = P OR T = R) THEN PRINT
T;” CLEAN”
490 PRINT “ROOM?”
500 INPUT 5
510 IF 5 < 1 OR S > 4 THEN GO TO 500
520 CLS
530 LETM=M- 9
540 IF ABS(S - R) = 2 THEN LETM=M-G
550 IF M < 0 THEN GO TO 600
560 LET R = S
570 GO TO 170
600 PRINT “OUT OF TIME”
610 PRINT “G:”;G,”P:”;P
620 STOP
700 PRINT “ТІМЕ-”;М
To run, key GOTO 100. Do not use RUN.
July/August 1981
for and by setting up an appropriate display
for the top of the screen this program
could be used as a basis for a "treasure
hunt," "spy" or similar game where it is
necessary to locate something that is
hidden.
Sample Run
ROOM=4 TIME=24
SEARCH?
CY? = NZL)
i-GUN
2-PRINTS
3-BOTH
Се = NZL)
GUN FOUND
ROOM?
( 71" - МИ
ROOM=2 TIME 5
SEARCH?
(ју: =
i~GUN
2-PRINTS
3—BOTH
(0787 = NZL)
i CLEAN
Коом?
(0557 = NZL)
OUT GF TIME
6:4
МИЦ.)
Piu
ROOM=2
SEARCH?
(^Y? = NZL)
i -GUN
2-FRINTS
5-БОТН
TIME=16
f аста
( = NL
GUM FOUND
FRINT&S FOUND
ТТМЕ=8
37
A Parallel Interface for the
7Х-80/МісгоАсе Computer
Alger Salt
Introduction
Almost everyone who owns a computer will ask or be
asked, “What sort of practical things can it do?” One of the
most obvious practical applications is controlling external
devices; however, few microprocessors or CPUs are designed
to do this directly.
Most manufacturers of microprocessors offer devices called
peripheral controllers which are integrated circuits designed
to be compatible with their particular CPU. These controllers
greatly simplify the task of interfacing external peripheral
devices such as disk drives, terminals, and printers. Fortunately,
the engineers at Sinclair Research Limited chose to design
their microcomputer around the Z-80 CPU which is well-
supported by several excellent peripheral controllers. One of
these, the Z-80 PIO can be used in constructing a simple
parallel interface for the ZX80/MicroAce computers.
Overview of the Z-80 PIO
The Z-80 PIO is a 40 pin integrated circuit designed to
serve as a simple direct, TTL compatible interface between
the Z-80 CPU and peripheral devices employing parallel data
transfer. (See Figure 1.) Communication between the PIO
and the CPU is accomplished by connecting the PIO data
lines directly to the CPU data bus. The PIO is a two-port
device. This means it can send and/or receive two sets of 8-
bit parallel data. Control lines on the PIO select one of the
two ports (B/A SEL), enable the PIO (CE), and allow the PIO
to differentiate control words from data words (C/D SEL).
Three other control lines (M1, IORO, RD) insure proper
timing sequences during CPU I/O operations. The bars over
the signal names indicate that they are active low.
Each port has two control lines used to establish handshaking
between the PIO and the peripheral device. These two control
lines (RDY and STB) are sometimes, though not always,
necessary to synchronize data transfer. In other words, one of
these control lines, the RDY line, may be activated to tell a
device which is sending data to the PIO, “Do not send data
now. Гат not ready... O.K., now I am ready. Send data.” The
device may respond by activating the STB line, “O.K., here is
the data. Get it now so I can do something else.” By using the
handshake lines, communication is established between the
PIO and the peripheral device resulting in an orderly, efficient
transfer of data.
Alger Salt, East Carolina University, Chemistry Department, Greenville.
NC 27834.
38
The PIO contains a number of internal registers used to
control its operation. The most important is the 2-bit mode
control register which can be programmed to select one of
several operating modes on port A or port B.
The PIO may be operated in one of four modes, designated
mode 0 through 3. Mode 0 is the output mode; all eight lines
on the designated port are output to a device. In mode 1, the
input mode, all lines on the port are input from a device.
Mode 2 is the bidirectional mode and is restricted to port A.
In this mode the handshake lines of port B along with the port
A handshake lines are used to control the flow of data in both
BUS k 8 I/0
PORT A
сво С Z-80 PIO
LINES TORQ
INTERRUPT IEI 1/0
CONTROL
LINES ТЕО РОВТ В
Figure 1. Functional Diagram of 7-80 PIO.
directions on port A. Mode 3, the control mode, is a hybrid of
the input mode and the output mode; any line of the specified
port can be designated as input or output. The control mode
differs from the bidirectional mode in that once a line is
designated as input or output, it stays in that condition and
reprogramming is necessary to alter the direction of data
transfer on that line. The handshake lines are not used in
mode 3. A more detailed explanation of the Z-80 PIO operating
modes can be found in references 2, 6 and 7 at the end of this
article. This discussion is restricted to the control mode
(mode 3). Other control registers internal to the PIO are used
to store interrupt vector addresses, a distinguishing feature of
the Z-80 PIO.
SYNC Magazine
Let us now see how to construct and program a parallel
interface for the ZX80/MicroAce computer, using this Z-80
PIO under non-interrupt, non-handshake control.
Construction of the Parallel Interface
Figure 2 shows a schematic diagram of the parallel interface.
Port B is used for input to read the states of eight toggle
switches (S1-S8) while port A is configured for output to drive
eight light emitting diodes (D1-D8). Inverters are used to
buffer the output port. The maximum output current capability
of the PIO port data lines is about 1.5 milliamperes, not
enough to drive an LED but enough to drive one TTL input
or about four low power Schottky (LS) TTL inputs. The
inverted system clock, ®, is available at pin #6B on the back
of the computer board. This signal is inverted again before
being presented to the PIO. The handshake lines, STB and
RDY, on each port are not connected. They are not needed
because operating mode 3 will be selected. Since this application
does not require interrupts, the IEI (Interrupt Enable In) line
is tied high and the IEO (Interrupt Enable Out) is not con-
nected.
Signals on the edge contacts of the computer board can be
brought out through a cable using a modified 50-pin edge
connector with 0.1 inch spacing between contacts (i.e., 3M
part #3439-1000). The connector must be modified because it
is closed ended and the computer requires an open ended
version. The modification can be done with a sharp knife or a
small saw.
The parallel interface circuit should be constructed on
some sort of plug-in circuit board for easy inspection and
modification. A high quality plug board such as Vector’s
4677-2DP works well since it provides an etched power and
ground bus. Etched pads for mounting dual-inline-plug (DIP)
integrated circuits are also provided. All ICs should be socketed.
Interconnections can be made by soldering small wires to the
pads or by wire wrapping or a combination of both. I recommend
the latter method: solder all power and ground lines to the
appropriate pins on the wire wrap IC sockets and wire wrap
control, data and address lines. Locate 0.1uF capacitors at
each IC package, connected between +5V and GND, to
decouple power supply spikes and suppress high frequency
oscillations on the supply.
A suitable enclosure for the interface can be purchased
from most electronic supply companies. It should be large
enough to house a separate power supply which is required
for operation of the interface. The circuit and power supply
could also be mounted on a flat piece of material, such as
aluminium or plexiglass, “open face” style.
There are two basic options for handling the power supply.
If you are planning to add more circuitry to your system later,
you should buy or build a relatively high current power
supply. A schematic for a +5V, ЗА power supply is shown in
Figure 3. The regulated portion can be used to power the
interface. The unregulated portion can be used to run the
computer if you want to eliminate the standard calculator-
type power supply. However, if you are not planning to add
more active circuitry and you are satisfied with the calculator-
type supply, you can get by without a separate supply. You
will need though, a +5V voltage regulator to regulate the
rough +9-11V going to the computer down to +5V for
powering the interface which requires a total of about
100mA.
July/August 1981
D6 3
«TU D6 А Roy HS
~<a | {> А/В SEL
А1
«c-r С sEL
4
i
2-80 PIO
о
о
со
—
о
со
z|
|
v
Y А
Е 25262536222
OV 1
— <=> GND 17 -
1
1
Џ
2X-80 / бабе | ~ 24 |26
MicroAce and edge i +5ү
computer connectors -І А
| 1 (from Fig. 3) | > |
Џ
1
! í |
i Parallel interface board 16 pin DIP "Real world"
‘connectors external
device
Figure 2. Schematic diagram of parallel interface circuit showing port A
I/O lines being used as inputs and port B I/O lines as outputs. (Note: The
software driver routine mentioned in the text assumes the opposite
configuration; port A is output and port B is input.)
51 ( +10 V
wy 3
PARTS LIST FOR POWER SUPPLY
T1-18VCT 4A Transformer Radio Shack 273-1514
D1,D2- 400 PIV 3A Silicon diodes 276-114
RI- 1 ohm , 102, 10 watt resistor |
010- 1М323 +5V regulator
€1-4400 mF 25V electrolytic capacitor
22-10 mF 25V tantalum capacitor
C3-0.1 mF ceramic disc capacitor
Figure 3. Schematic diagram of power supply used to operate the computer
and the parallel interface circuit.
39
Figure 5. Тһе inside of the author’s system. The parallel interface and
extra memory are located on the expansion board mounted above the
computer.
Figures 4, 5 and 6 are photographs of the author’s MicroAce
system. The power supply provides unregulated +10V for
the computer and 2K of on-board memory, and regulated
+5V for the parallel interface plus an additional 6K of memory
on the expansion board which is mounted just above the
computer. The entire system is housed in a steel enclosure
fitted with a hinged lid to which a standard size keyboard is
mounted. The parallel port I/O (input/output) lines and
handshake lines are brought out through two 16-pin DIP IC
sockets. The cassette I/O connections are made available
through two isolated phone jacks mounted on the front of the
enclosure. Two RCA type phono jacks bring out the video
signals: one for driving a standard video monitor and one for
the RF modulator. Since the modulator is external to the
computer, I use a TV as a video monitor for my other
computer (Exidy Sorcerer).
40
Figure 4. Author’s 8K MicroAce system connected toa
standard video monitor and standard size keyboard.
The bread board in the foreground holds 16 LEDs
which are used to monitor the outputs of both ports.
Figure 6. The inside with the expansion board removed, revealing the
computer board.
Programming the PIO
Since the ZX80 version of Basic offers no direct means of
communication with an I/O device, a driver subroutine coded
in Z-80 machine language must be loaded into memory to
operate the PIO. Data and control words can be passed from
Basic to the driver routine through the POKE instruction.
The routine is executed by calling it with a USR instruction.
Some knowledge of the Z-80 CPU instruction set is helpful in
understanding the driver routine.
Data is transferred from the CPU to the PIO by addressing
one of its internal registers and writing to it by using one of
the Z-80’s OUT instructions. We need only be concerned
with four of the PIO registers in this application: port A
control, port B control, port A data, and port B data. Each
register is accessed by a unique address. I/O instructions are
always associated with one-byte addresses comprised of the
SYNC Magazine
lower 8 bits of the address bus. A minimum of 3 address bits is
required to operate the PIO. Normally, address line АО is
connected to the port select line (B/A SEL) of the PIO and
address line А1 is connected to the control/data select line
(C/D SEL). The six remaining bits of the address byte are Address Meaning
decoded to select one of a number of I/O devices. Since the
PIO is the only I/O device in this system, decoding is not Binary Hexadecimal* Decimal* Contents of
necessary. As shown in the schematic (Figure 2), address line Accumulator
A7 is inverted and connected to the chip enable line (CE) of interpreted as...
the PIO. Therefore, any address within the range 10000000B ІХХХХХ00 80 128 data — portA
(B stands for binary) 11111111B will enable the PIO. The 1ІХХХХХО1 81 129 data — port B
machine language driver routine (Figure 7) uses the “output IXXXXX10 82 130 control — port A
immediate From Accumulator” instruction to transfer a byte IXXXXX11 83 131 control — port B
of data to the PIO. This instruction is represented OXXXXXXX 00 0 PIO is not enabled,
mnemonically no change
OUT(n),A
It transfers the contents of the Accumulator of the A register X means "don't саге”; this bit can be 1 or 0. * These values assume that
(one of the Z-80 CPU internal registers) to the I/O device X —0.
addressed by n. The table in Figure 8 gives the addresses of
the PIO internal registers and their significance when using Figure 8.
the OUT immediate instruction in this configuration.
Label Location Machine code Mnemonic Comment
(Dec) (Hex)
0 0 00 NOP Do nothing.
1 0 00 МОР Do nothing.
2 62 ЗЕ. LD A, СЕН Load register A with operating
3 207 СЕ mode control word.
4 211 D3 OUT (82H), A Send control word to port A
5 130 82 control register.
6 62 ЗЕ LD A, 00H Load register A with data
7 0 00 direction word. All lines output.
8 211 D3 OUT (82H), A Send data direction word to
9 130 82 port A control register.
10 62 ЗЕ LD А, СЕН Load register A with operating
11 207 СВ mode control word.
12 211 D3 OUT (83H), А Send control word to port B
13 131 83 control register.
14 62 3B LD A, FFH Load register A with data
15 255 ЕЕ direction word. АП lines input.
16 211 D3 OUT (83H), A Send data direction word to
17 131 83 port B control register.
18 62 JE LD A, 07H Load interrupt control word.
19 07 07
20 211 D3 OUT (82H), A Send interrupt control word to
21 130 82 port A control register.
22 211 D3 OUT (83H), A — Send interrupt control word to
23 131 83 port В control register.
24 201 C9 RETN Return to Basic program.
22 62 ЗЕ LD A, 00H Load register A with the
26 00 00 contents of this location.
27 211 D3 OUT (80H), A Send contents of register A
28 128 80 to port A data register.
29 201 C9 RETN Return to Basic program.
30 33 21 LD HL,, 0000H Clear the HL register pair.
31 0 00
22 0 00
23 14 ОЕ LDC, БІН Load register with port B
34 129 81 data register address.
35 231 ED IN L, (C) Read port B I/O lines. Load
36 104 68 data into register L.
37 201 C9 RETN Return to Basic program.
СС „ЭА А ee a ee Е EE SEEE O
Figure 7.
July/August 1981 41
Before data сап be sent through a port, certain control
words must be loaded into the internal registers of the PIO.
This process is called initialization, and the code that does
this is called the initialization routine. Several things must be
done in the initialization process: the operating mode must be
set, the data direction must be established, and the interrupt
servicing must be taken care of. In this example the selection
of mode 3 simplifies matters since the handshake lines are not
used. The operating mode is selected by writing a control
word with the four least significant bits set high. The two
most significant bits determine the opterating mode and the
other two bits are not used as shown in Figure 9.
Operating Mode Control Word
Binary Hexadecimal Decimal
Output О OOXX1111 0 15
Input 1 OIXX1111 4F 79
Bidirectional 2 10XX1111 SF 143
Control 3 11XX1111 CF 207
Figure 9.
When the control mode (mode 3) is selected for a particular
port, the next control word sent to that port will define the
direction of data transfer on each of the port’s I/O lines. Each
line corresponds to a bit position in the control word; the
most significant bit of the control word corresponds to the
most significant I/O line. A high condition (1) means input
and a low condition (0) means output. For example, suppose
the control word FOH (H stands for hexadecimal) is used to
select data direction on the port B. Lines PBO through PB3
would be set up for output while lines PB4 through PB7
would be set up for input.
Interrupts are handled very conveniently in this application;
they are disabled by simply writing 07H (00000111B) to the
control registers in both ports.
The PIO machine language driver routine listed in Figure
7 may be located in the unused spare portion of memory.
However, in order to save the driver on cassette tape it must
be located in the variables area of memory which is located
immediately following the user Basic program. (When a program
is stored on tape only the program itself, system variables and
program variables are saved; not all of memory.) The two
memory locations 16392 and 16393 contain the low byte and
high byte, respectively, of the starting address of the variables
area. This address will be referred to by the symbol ORG
which stand for origin. Since the value of ORG depends on
the size of the Basic program, all addresses in the driver
routine must be relative to ORG.
The driver consists of three machine language subroutines,
each ending with a return from subroutine instruction. The
first routine initializes the PIO, setting up port A for output
and port B for input. (Note: This is opposite to what is shown
in the schematic diagram of the parallel interface. This means
that the switches should be connected to port B and the
inverter-buffer inputs should be connected to port A.) The
interrupts are disabled in the last portion of the initialization
routine. Another routine sends a selected byte of the port A
output routine. It is altered by the execution of a POKE
instruction in the Basic program. The third routine, the port
B input routine, reads the data present at the port B I/O lines
and stores the information in the L register. The HL register
pair is cleared, set to 0, at the beginning of the routine.
Storing the data in the L register is convenient because, when
a USR function is called, the value of the HL register pair is
returned. For example, suppose that during execution of a
Basic program the statement LET X=USR(Z) is encountered,
42
where Z is equal to the starting address of a machine language
routine that merely loads the value 31264 in the HL register
pair. The variable X would then be equal to 31264 after the
completion of the machine language routine. If the HL register
pair was not altered during the routine, X would equal Z.
The Basic program that calls the driver routine must provide
a means of entering the machine language code. Getting the
code into the variables area is done by setting up an array,
i.e., allocating a portion of memory (large enough to hold the
driver) with a DIM statement. Getting the proper code into
the array can be done in several ways. The simplest is to enter
the elements as signed integers. Be aware that the integers
are stored in two bytes of memory, with the less significant
byte first. This makes it very difficult to decipher the machine
code. A more elaborate method involves writing a Basic
monitor which would include a hexadecimal-to-decimal routine
and a decimal-to-hexadecimal routine for entering and displaying
one-byte entries in hexadecimal notation. This would require
perhaps more memory than a 1K machine could accommodate,
but inspection and modification of the machine code would
be much easier. The Basic program in Figure 10 employs the
former method for entering the code.
10 DIM MCZO)
20 LET Vzl16392
30 LET ОББ=РЕЕК (V0 +РЕЕК (V+1) #25642
40 LET @0s0RG+25
50 LET BI-ORGeZO
60 LET MLA=AC+ i
70 PRINT
BO PRINT
90 PRINT
1900 PRINT "MENU"
120 PRINT "1) INFUT CODE"
150 PRINT "2) REVIEW CODE"
140 PRINT °"3) FORT eA GUT"
150 PRINT "4) FORT -B- Th"
160 INFUT à
170 LET ба Жі ООО
180 CLS
i720 GOSUB а
jooo0 FOR Io TO 20
того PRINT I
10940 INFUT MIO
1060 NEXT I
Logo RETURN
20900 FOR 121 TO 20
голо PRINT I+GRG,FPEER (1+0RG),1+0RG+21,
PEER (i+0ORGt21)
зоо NEXT I
2060 INFUT 2%
гово RETURN
2000 PRINT "ENTER BYTE OUT"
2020 INFUT В
S040 FORE MLA, Е
aUOSO0 LET *=U5R (ORG)
JOBO LET Х=ОВЕ taco
2100 FRINT "ANOTHER BYTE 7"
S120 INFUT 2%
S140 CLS
21609 ТЕ МОТ Z$-"" THEN RETURN
2180 GOTO 2000
4000 PRINT "HIT МЕМ LINE TO READ FORT B"
4020 INPUT 2%
4040 CL 3
4oà60 IF NOT Z$-"" THEN RETURN
2080 LET X=USR ЈЕО)
4100 LET X-USRt(BI
4120 FRINT "рата AT FORT В... "Хх
4140 8070 4000
ги
Figure 10.
SYNC Magazine
This Basic program is menu-driven, giving the user the
following options: entering the machine code, reviewing or
listing the machine code, entering the byte to be sent out
through the port A I/O lines, and reading the data present at
the port B I/O lines. The variables used in the program are
listed in Figure 11. The Sinclair version of integer Basic
allows variables to be used as labels for GOTO and GOSUB
statements. This feature is absent from many “expensive”
versions.
Variable Meaning
ORG Beginning of driver routine.
AO Beginning of port A output routine.
BI Beginning of port B input routine.
MLA Location of byte to be output through port A.
У,У-+1 Points to the beginning of the variables area.
Figure 11.
Remember, when you get the driver routine loaded into
memory, either by hand or by tape, do not press RUN.
Instead, press GOTO followed by a number less than or equal
to the lowest line number. GOTO 1 is safe.
Operation of the program is straightforward. The user is
first shown a menu and is prompted to input a number
between 1 and 4. If 1 is entered, the user is prompted to enter
the signed integer elements which comprise the machine
code. In this program the user should respond with the
following integers. The screen is cleared after each entry.
Display Enter Display Enter
0 0 10 -32045
1 -12482 11 -31789
2 -32045 12 16073
3 62 13 -11386
4 -32045 14 -13952
5 -12482 15 33
6 -31789 16 3584
7 -194 17 -4735
8 -31789 18 -13976
9 1854 19 0
20 0
Figure 12.
Item 2 on the menu displays the contents of the array in
which the driver routine is buried. Item 3 asks the user to
input an integer, between 0 and 255, to be output through the
port A I/O lines. For example, if the integer 255 is entered, all
eight I/O lines will be set high; if 0 is entered, all lines will be
set low. Selection of item 4 will read the port B data present
at the port B I/O lines. If lines 0 and line are high and the
others connected to ground, the decimal value “129” will be
displayed. One way to exit the program is to break (hit the
space key) while the screen is blank. Another way is to enter
the letter “7” when the computer is expecting an integer
input, indicated by the appearance of the cursor in
inverse video.
Applications
The number of possible applications for the ZX80/MicroAce
with a parallel interface is limited only by the user’s imagination.
With 16 I/O lines, interfacing devices such as A/D (analog to
digital) and D/A (digital to analog) converters to the computer
is a possibility perhaps once thought unachievable by many
ZX80/MicroAce owners. Control of high voltage-current devices
is also possible with relays and relay driver circuits.
With an A/D converter one could realize an inexpensive
data acquisition system for monitoring and recording various
quantities in the laboratory, in industry, or in the home. For
July/August 1981
instance, a temperature to voltage or temperature to current
converter could be connected to the A/D for recording
temperatures over a period of time at specified intervals. The
calibration could be done in software to reduce hardware
costs. Of course, a simple voltmeter would also be a useful
application.
A programmable voltage source or power supply could be
constructed by connecting a D/A converter to the parallel
interface. Complex waveforms can be generated by cycling
through a table of data words to be output by the D/A thus
providing the user with a programmable function generator.
An A/D converter can even be realized by using а D/A and a
voltage comparator in a configuration known as a successive
approximation A/D converter.
High
voltage
source
High
voltage
PARTS LIST FOR HIGH VOLTAGE-CURRENT CONTROL CIRCUIT
Rl- 220 ohm 1/4watt resistor =
R2- 2.2K onm 1/4watt resistor
- TIL113 optical coupler
01- 2N3055 transistor
01- 1N4001 diode
11- Relay (Potter-Brumfield KRP11DG)
Figure 13. Schematic diagram of relay and computer controlled, optically
isolated relay driver circuit.
Figure 13 shows a circuit that enables computer control of
high voltage-current devices such as televisions, coffee makers,
and lights, (NOTE: Use caution if you decide to build this
circuit. All high voltage wires and connections should be
isolated and insulated from the user and the computer circuits).
In this circuit an output line from one of the inverting buffers
is used to drive an optically isolated relay driver circuit. An
optical coupler with a darlington transistor output is used to
isolate the computer circuits from any high voltages which
may appear. The darlington output provides higher current
driving capability than a standard, single transistor optical
coupler but at the sacrifice of speed which is of no consequence
in this application. Any comparable relay with a 12 VDC coil
will also work. Be sure to stay within the current ratings of the
contacts, however. Relays with other DC (direct current)
voltage ratings will also work with appropriate resistor-value
substitutions in the circuit.
As I said, the possibilities are limitless. You may decide to
just let the computer turn on LEDs in random sequence. At
any rate, I hope you will experiment and share your discoveries
with others via SYNC.
Selected References
1. Artwick, Bruce. Microcomputer Interfacing. Prentice-Hall, 1980.
2. Barden, William Jr. The Z-80 Microcomputer Handbook. Howard
W. Sams and Co., 1979.
3. Engineering Staff on Analog Devices, Inc. Analog-Digital Conversion
Notes. Analog Devices, 1976.
4. Nichols, Elizabeth; Nichols, Joseph; Rony, Peter. Z80 Microprocessor
Programing and Interfacing. Books 1 and 2. Howard W. Sams and Co.,
1979.
5. Salt, Alger. “Build Additional RAM.” Syntax 2, no. 3 (March 1981).
6. Z80 Assembly Language Programming Manual. Zilog, 1977.
7. 2-80-РТО Z80A-PIO Technical Manual. Zilog, 1977.
See SYNC NOTES for a P.S. from the author.
43
receptical
If you have spent much time looking at
the schematic for your ZX80 or MicroAce,
and if you have had the opportunity to
compare it with schematics for other home
computers, you probably have noticed
that there are considerably fewer parts.
This is due to the efficiency of circuit
design in several areas. One of these areas
involves the absence of separate character
generator ROMs in the video circuitry.
The character generator is contained
in the same ROM that holds the Basic
interpreter. Sixty-four eight byte blocks
are located in addresses 3584 to 4095 (0Е00
to OFFF hex). While the Z X80 is in the
video display mode, the CPU is addressing
these memory locations and loading the
data into IC9 (U10 for MicroAce). This
data transfer is parallel, or eight bits at a
time. The data is then shifted serially, or
one bit at a time. These bits go to the
video modulator which causes either light
or dark spots on screen, depending on
whether the bit is a *one" or "zero." The
IC21 (U14) keeps track of which byte is
to be addressed by counting up to eight
horizontal sync pulses to determine which
of the eight horizontal lines for each
character is being displayed.
You can examine each of the 64 char-
acters in more detail by using the following
program.
10 INPUT AS
20 LET A=(CODE CAS) жб) +5584
50 FOR X=@ TO 7
40 LET С=РЕЕК (A+X)
50 FOR Y=@ TO 7
БО LET Ес2жж(7-Ү)
70 IF С=Е ОК DE THEN GO ТО 100
8 PRINT " "3
за GO TO 120
100 LET С-С-Е
110 PRINT СНК$ (128);
120 МЕХТ У
1:20 PRINT
140 NEXT X
PRESS RUN and NEWLINE. Then press
any Key and NEWLINE.
Dennis Duke. 716 Torri Ct.. Aledo. TX 76008.
44
Mini-Billboard
Dennis Duke
HE HL»
= TM
Press RUN and NEWLINE. Then press
any key and NEWLINE.
Line 20 converts the character A$ into
the address of the first byte for that
character in ROM. Line 40 sets C equal
to the decimal value of that byte which is
between 0 and 255 inclusive. In the first
pass of the FOR-NEXT loop in lines 50 to
120, C is examined to determine if the
most significant bit (MSB) of the data is a
"one" or a "zero." If the MSB is a “zero,”
a space is printed. If the MSB is a “опе,”
an inverse space is printed. In the next
pass, the second most significant bit is
examined and printed. The last pass will
examine and print the least significant
bit.
After eight bits have been printed, line
130 causes a new line so the next byte can
be printed directly below the first. The
FOR-NEXT loop in lines 30 to 140 causes
eight bytes from sequential addresses to
be printed.
The addition of another FOR-NEXT
loop, an array, and some other modifica-
tions to this program allows us to print an
eight character string on two rather large
lines to create a "Mini-Billboard" on the
TV screen.
Mini-Billboard
5 DIM AtS)
10 INPUT AS
15 FOR Ісі TO &
20 LET ACT) =CCODE (A$) ж8 3 +5584
21 LET AS=TLS CAS)
TU 7
TO L
; PEEK (ACI}+X)
од FOR Y=0 TO 7
—Z*xekRC7-Y)
70 IF C=E OR COE THEN GO TO 100
ЕЙ PRINT " ";
30 GO TO 128
100 LET C=C-E
110 PRINT СНК C129) 5
120 NEXT Y
150 NEXT I
140 NEXT X
150 LET Е=Е+4
1&0 LET ізі зд
170 IF L-& THEN GO TO 30
Hou Uw n m:
то ~
C4
S
n
О
ж
(e зе Го
Press RUN and NEWLINE. Then enter
READ SYNC (or any two four letter words)
and NEWLINE.
You probably noticed we no longer
need a PRINT statement in line 130 since
four groups of eight characters are now
printed in a line which will cause an
automatic new line by coming to the end
of a 32 character line. If you want to use
a different graphic, change the number in
line 110. Try also 7, 136, 8, and 223.
So now you have a program which will
print two large, four letter words on your
TV screen. This may lead to some inter-
esting suggestions from your friends, but
have fun with it anyway. "n
SYNC Magazine
Hardware Review
Anyone with a Sinclair or MicroAce has experienced the
hassle of having to check the TV screen after every entry to
see if it got into the machine. Of course, there are those
people with good peripheral vision who can manage this feat
without bobbing their heads, but not me. So when I saw an ad
for a “keyboard beeper,” I realized this most certainly would
be a big help in entering programs on the membrane keyboard
and sent for one.
The beeper comes assembled and is extremely simple. It
consists of two integrated circuits, two resistors, and a capacitor
mounted to a P.C. board barely larger than the components.
The power and ground wires are connected to the ZX80
board just below the modulator on some wide power traces.
Joe Utasi, 2028 Knightsbridge Dr., Cincinnati, OH 45244.
Keyboard Beeper
Joe Utasi
Five wires (which were twisted into a bundle) go to the
keyboard side of the five pullup resistors at the extreme lower
left side of the board. The order of sequence does not matter,
as long as you connect to the side of the resistors that goes to
the keyboard and not power. It is easy to see which side goes
to the keyboard by just following the traces.
The last step is to install the small round piezo-electric
transducer which produces the sound. The directions provided
with the beeper suggest soldering one edge to the top of the
modulator (the left side), so that is where I put it. The one
remaining wire from the beeper board is soldered to the
white portion of the transducer. I used a piece of carpet tape
(not included in the package) to mount the beeper to the
inside of the case top on the front surface of the "blister."
The beeper worked perfectly the first time. Slight changes
in the tone of the beep for different keys can be detected.
This might be an asset if you have a good ear.
The real advantage comes when entering SHIFTed com-
mands. Programming seems to go faster with less aggravation
now that I know I am making good "contact" with the
keyboard. I would certainly recommend the beeper as a
definite improvement to the ZX80.
Keyboard Beeper, $12.
Burnett Electronics
908 Morris St.
Cincinnati, OH 45206 »"
The Colossal Computer Cartoon Book
Do
Computer
Enthusiasts
Have
More
The best collection of computer cartoons ever is now in
its second printing, and sports a bright new cover. The
fifteen chapters contain hundreds of cartoons about
robots, computer dating, computers in the office, home,
and lab, and much more. 36 cartoonists share their views of
man's ultimate machine.
Keep this book with your reference works. When
needed, the right cartoon can say it all for you. When you
need a break from debugging a good laugh can give you a
welcome lift. Recommended for hours of fun and comic
insight.
Edited by David Ahl, mastermind behind the April Fool's
issue of Dr. Kilobyte's Creative Popular Personal Re-
creational Micro Computer Data Interface World Journal,
this cartoon book contains much of that same incurable
zaniness. [Want this issue? It's April 1980 and only $2.50
postpaid].
ITS TIME
E
FICTION PROGRA
ON TV.
an "
FOR ?
YOUR FAVORITE SCIENCE |
м .
N |
THE ROBOTS
NEVER WIN.
| о
|
А large 8' x 11" softbound collection of 120 pages, it still sells for only $4.95. (6G).
July/August 1981
Hardware Review
SK Basic ROM
David Lubar
While the 4K Integer Basic in the Sinclair
ZX80 is adequate for many applications,
most programmers will eventually feel a
hunger for more power. True, advanced
functions can be simulated by way of
subroutines, but such measures eat memory
at an alarming rate. Enter the 8K Basic
ROM. The chip costs a mere $39.95, which
is an extremely low price for any ROM.
Some versions of Basic are sold for over
$200 on disk. Sinclair gets four stars for
not robbing its customers.
Plugging In
Installing the ROM chip requires opening
the Sinclair. Most owners have probably
already done this out of curiosity and
learned that nothing disasterous follows.
One really has to go out of his way to hurt
the little critter. The only problem is dealing
with the plastic pins which hold the case
together. Once the case is open, the old
ROM has to be removed. This requires
some patience. If a chip is pulled with
unequad pressure, the pins can be bent.
It’s best to keep the old ROM intact, for
reasons that will be covered later. The
new ROM is installed by lining up the
pins and exerting gentle pressure. Next, a
new keyboard overlay is put in place.
This overlay contains letters, numbers,
keywords, graphics symbols and functions,
with color coding to aid the confused.
Once the ROM has been tested by power-
ing up the computer, the case can be
replaced.
Features
With the ROM installed, the Sinclair
has floating point capability. It can handle
decimals with nine-place accuracy. Other
added functions include string and numeric
arrays of any dimension, trig functions,
and extended string functions. The PLOT
and TAB commands allow formatting of
text and graphics. Unfortunately, the
proposed DRAW command, which would
have drawn a line between any two sets
of coordinates, was not included in the
final version of the Basic.
46
As before, keywords are obtained with
a single stroke. By hitting the FUNCTION
key, the user can also obtain functions
with one keystroke. Don’t get excited about
the commands FAST and SLOW. The
Sinclair already operates in the FAST
mode. The SLOW mode (to eliminate
flicker of the display) only works on the
ZX 81, which is not yet available in the
U.S. There is a SCROLL command, which
moves the screen display up one line.
The computer will still crash if you attempt
to write beyond the screen.
Several commands have been provided
for use with the printer Sinclair plans to
introduce. The user will be able to send
listings to this printer and to print. the
contents of the screen. For interactive
programs, there is an INKEY$ command.
This reads the keyboard without requiring
NEWLINE. The pause command sends
the contents of the display list to the
screen and waits a specified amount of
time. This allows for limited animation,
but still produces a flicker. All in all, the
8K Basic greatly expands the potential of
the Sinclair.
Compatability
The 8K ROM contains an improved set
of tape routines. While this means that
loading and saving should be less hassle,
it also means that you can’t load old-
ROM tapes into a new-ROM machine.
And even if you could load such programs,
they wouldn’t run. This means most users
will be doing a lot of translating. Two
major differences must be kept in mind.
First, many programs took advantage of
the Integer Basic, ignoring the remainder
after division. To simulate this in the new
Basic, use the INT function. Secondly,
where the Integer Basic ROM used minus
one for true when evaluating logical
operations, the 8K ROM uses positive
one. Any calculations based on logical
operators will require a sign change during
translation.
Ideally, it would be nice to be able to
switch from one ROM ю the other.
Someone is bound to produce such a switch
in the near future and many enterprising
hobbyists are likely to design their own.
While such a switch would clobber anything
in memory, it would allow loading of either
flavor of tape without pulling and replacing
chips. For this reason, it is advisable to
hold onto the old ROM.
The most noticable difference between
the ROMs occurs when you try entering
a 1K program. The new ROM uses about
100 bytes more of RAM than the old
ROM. Most programs that fit into 1K
before won't fit now. To get any value
out of the new Basic, a user should have
at least 2K, preferably 16K.
So, if you are feeling limited by 4K
Basic, and either plan to expand memory,
or already have, then the 8К Basic ROM
is an excellent way to extend the capabilities
of your Sinclair. The 8K Basic ROM is
available for $39.95 plus $4 shipping from
Sinclair Research Ltd., 1 Sinclair Plaza,
Nashua, NH 03061. |
ЕТІЛ СР
This column will feature short programs
to show off your ZX80, impress your family
and friends, and tickle your imagination
when SYNC arrives at your place. We
invite your contributions. Address them
to SYNC, 39 E. Hanover Ave., Morris
Plains, NJ 07950.
10 LET M=16567
20 FOR A=386 TO 419
30 POKE M+A-386,PEEK(A)
40 NEXT А
50 POKE М-ҒА-386,201
60 ҒОК А-0 ТО 32767
70 PRINT A
80 LET B=USR(M)
90 CLS
100 NEXT A
Notes:
10 A few bytes after DF-END
20 Section in Basic to turn on screen
50 Return at end
Enter RUN and NEWLINE. You will have
to adjust the screen to get as good a
picture as possible, but it still will not be
perfect.
Our thanks to:
David Goodrich
124 NE Spruce
Bartlesville, OK 74003 n"
SYNC Magazine
Software Review
After the successful introduction of
Super ZX80 Invasion, [see SYNC 3:5]
Softsync has come out with Double Break-
out, its second active display game. Double
Breakout is just as much fun as Super
Z X60 Invasion, and even more challenging.
This, too, fits into 1К of memory.
After loading the game from the cassette,
the words “100 REM" appear at the top
of your screen. Enter “СО TO 1" and
then select your level of play. There are
seven skill levels where 7 is slow enough
for beginners, 4 is medium, and 1 is
extremely fast for the expert. Softsync's
brochure claims that you do not have a
chance at level 1, but we have found that
after extensive play you do have a good
chance.
A game field 31 spaces wide and 18
spaces high appears on the screen. Within
the area are two walls of blocks running
vertically, each five rows thick. One is in
the middle of the screen, and the other is
off to the right. The paddle appears in the
upper left hand corner of the screen and
can be moved up and down along the left
side by using the arrow keys (5 and 8).
The makers recommend that your com-
puter be turned sideways so the keys will
face up and down according to the move-
ments of the paddle, but we suggest that
you turn your television sideways if possible.
The ball, represented graphically by the
letter *0", bounces between your paddle
and the blocks, each time chipping a block
off the wall. Once you break through the
first wall there is another wall which you
must also knock out.
David and James Grosjean, 50 Kings Rd., Chat-
ham, NJ 07928.
July/August 1981
And the Walls Came >
David апа James
Grosjean
You have nine balls with which to knock
out the blocks. The number of balls
remaining is displayed in the left hand
corner of the screen, just outside of the
playing area. Each time you miss the ball,
the number diminishes by one, and the
next ball is served immediately. If you
lose all the balls, a new game is started,
and, if you successfully clear out all the
blocks, the ball continues to bounce
around.
Q
%у, Ming
Down
You cannot stop the game to change
skill levels during play. The BREAK key
does not function. You must unplug the
machine and reload the game.
By deleting line 100, the portion of the
program written in Basic is revealed. This
is the part which asks for the ball speed
and then calls a machine code subroutine
which actually plays the game. Line 450
of the program makes sure you do not
enter a speed slower than 7 or faster than
1. If you delete this line, you can enter a
speed slower than 7. The game will run
the same as before even with line 100
missing.
For those of you who play the original
arcade Breakout games by Atari, here
are a few comparisons: The name Double
Breakout does not mean two balls and
two paddles, like Atari’s, but two walls of
blocks. This could be confusing. In Atari’s
arcade Double Breakout, the ball increases
speed as it hits more blocks, but in this
Double Breakout the speed you choose
at the beginning of the game remains the
same. Softsync's Double Breakout gives
nine balls with automatic serving, while
the arcade game gives only three balls
with manual serving. Double Breakout
serves a new ball as soon as one is lost, so
on level 1, if a ball is lost, the next one
will be served so quickly, that you might
not be able to get to it in time return it.
One shortcoming of the game is that
there is is no scoring, and another is that
there is no extended play such as extra
balls or walls.
Double Breakout is another break-
through in creating active display games
for the ZX80. We had great fun playing
Double Breakout and are amazed at how
much they fit into 1K. a”
47
ДЕ | | {в = — ПО
Software
ZX80/MicroAce software on cassette:
Dragon Castle Adventure, Betting Sys-
tem for Horse Players, Robot Composer,
and ESP Guessing; all 4 for $10.
Cecil Bridges
1248 N. Denver
Tulsa, OK 74106
Three cassette tapes: (1) Slot Machine,
Robot Fight, Corporation, Tank Battle;
(2) Lucky Lindy, Crop Duster, Nuke
Em, Carrier Landing; (3) The Pharaohs
Treasure; $10 each.
Tensor Technology Inc.
P.O. Box 17868
Irvine, CA 92713
Smart Reversi | Othello]. Play the classic
game against your Z X80. Uses a very
strong move algorithm extracted from
a much larger program; game board
display. (Othello [R] is.a trademark of
CBS Toys, Inc.) $6. £3.50 (U.K.)
C. W. Percival
193 Peaceable St.
Ridgefield, CT 06877
The ZX80 Companion is now available
with a 20 pp. supplement for the 2.Х81.
The supplement is available separately
for £1.50.
Linsac
68 Barker Road
Linthorpe
Middlesbrough, Cleveland, TS5 5ES
England
ZX80 Multiple Line Statements
Easy, Useful Programming Trick.
Saves memory, runs faster. Details £1
inc. postage (U.K.) or $2.50 inc. airmail
(USA).
Tim Humphries
16 Coniston Road
Sutton Coldfield
West Midlands
England
ZX60 Graphics; 48 pp. containing pro-
gramming techniques and 6 original pro-
grams; $8 incl. postage.
SUMWARE
P.O. Box 30
Shawville, PA 16873
48
ZX80/1 Record; a tape record system
to save, load, or enter new 96 byte
records; ideal for addresses; for all ІК
machines (4K/8K КОМ); £3; $9. Direc-
tory; a simple program to read tapes
and display program names; (8& ROM);
£2; $6.
Logan Software
24 Nurses Lane
Skellingthorpe
Lincoln LN6 OTT
UK
Music cassette: Side A: Player ZX80;
Side B: space MUSE-AK, a random
sound program. Prepaid orders; $6.95
postpaid ($10 outside the U.S.). Other
programs available.
William Don Maples
688 Moore St.
Lakewood, CO 80215
5 cassettes: (1) Games; (2) Junior Edu-
cation; (3) Business and Household; (4)
Games; (5) Junior Education; £3.95.
Designed for the 7Х81, but many will
run on the ZX80 with SK ROM; some
need the 16K RAM pack. Cheque/PO;
Access/Barclaycard.
Sinclair Research
FREEPOST 7
Cambridge, CB2 1YY
UK
® Microcomputer Index; subject index-
ing of articles in 20 microcomputer peri-
odicals.
Microcomputer InformationServices
2464 Е Camino Real
Box 247
Santa Clara, CA 95051
Filing program “Мише”; £17.50.
Machine code assembler “ZXAS” for
ZX80 or ZX81 (specify); £3.95.
Bug-Byte
251 Henley Road
Coventry CV2 1BX
England
Compute and display program (ІК &
2K) with instruction booklet, coding
sheets, and coding charts for ZX80 (4K
ROM); £4.95.
JRS Software
19 Wayside Avenue
Worthing
West Sussex, BN13 3JV
England
e Wide range of games for ZX80/1 (4K
& 8K ROM).
Premier Publications
12 Kingscote Road
Addiscombe, Croydon,
Surrey
England
e 2 versions of Defender with built in
software to drive their soundboard (£25);
£4.50 small screen; £5.50 large screen.
Quicksilva
95 Upper Brownhill Road
Maybush, Southampton,
Hants
England
Hardware
Re-Zolv Resist. Used with positive or
negative transparencies; circuit patterns
can be drawn also; develops with water.
For the hobbyist and the professional
engineer. Starter kit: COD $13.40; $12
for prepaid. Phone (217) 352-9336.
Coval Industries, Inc.
2706 W. Kirby Ave.
Champaign, IL 61820
MicroAce upgrade products:
ЗК КОМ; $35.
Video upgrade board for flicker free
display (8K ROM required); $29.50.
MicroAce 2K Computer Kit; $149.
Planned for the fall: 16K RAM, $150;
4K RAM, $110.
MicroAce
1348 E. Edinger
Santa Ana, CA 92705
Users Groups
ZX80 Southeast Region Club
869 Levitt Parkway
Rockledge, FL 32955
Newsletter planned beginning in August.
Pres. Ralph Coletti. Inquiries from
interested parties welcome.
SYNC Magazine
Se ad
creative
compating
Creative Computing-- Albert Einstein in
black on a red denim-look shirt with red
neckband and cuffs.
Га rather
<> be playing
l'd rather be playing spacewar-- black
with white spaceships and lettering.
Computer Bum-- black design by car-
toonist Monte Woiverton on gray
denim-look shirt with black neckband
and cuffs.
Creative’s own outrageous Bionic Toad
in dark blue on a light blue shirt for
kids and adults.
Give your
tie a rest!
АП T-shirts are available in adult sizes
S,M,L,XL. Bionic Toad, Program Bug and
Spacewar also available in children's sizes
5(6-8), M(10-12) and L(14-16). Made in USA.
$6.00 each plus 75€ shipping.
Specify design and size and send payment
to Creative Computing, 39 E. Hanover Ave.,
Morris Plains, NJ 07950. Orders for two or
more shirts may be charged to Visa, Master-
Card or American Express. Save time and
call toll-free 800-631-8112 (in NJ 201-540-
0445).
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Beware the
Program BUG!
from Katie and the Computer
The Program Bug that terrorized Cyber-
nia in Katie and the Computer is back
on this beige t-shirt with purple design.
You can share the little monster with
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Plotter display of Pi to 625 Places in
dark brown on a tan shirt.
Crash Cursor and Sync from the comic strip
in SYNC magazine emblazoned in white on
this black shirt.
Roll down the block with this little
black Robot Rabbit (on a bright orange
t-shirt) оп your back and you can
intimidate every carrot, radish or cuke
in your way.
...А ЭСТЕМСЕ -
FICTION
CARTOON
COMEDY
SERIES IN
EVERY ISSUE
THRILL TO THE INSANE ADVENTURES OF --
"
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17
"
Tut
* «И
PLUS:
Articles,
games,
applications,
reviews and
MORE!
Brought to you by the people at
creabive compating
SYNC is the dynamite bi-monthly magazine for users of the Sinclair 2Х80. The main
focus is on applications, programming techniques, hints and tips for getting the most
out of the ZX80. SYNC also reviews new peripherals, software and books for the ZX80.
· Subscriptions to SYNC cost just $10 for Six bi-monthly issues (£10 in the U.K.). Send to
SYNC, 39 E. Hanover Avenue, Morris Plains, NJ 07950, USA.
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